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Now you see it, now you don't: what optical illusions tell us about our brains

Illusions can offer insights into how the visual system processes images.

Maurits Escher: where do the staircases lead?

The human brain is a network of about 20 billion neurons – nerve cells – linked by several trillion connections. Not to mention glial cells, which scientists used to think were inactive scaffolding, but increasingly view as an essential part of how the brain works. Our brains give us movement, language, senses, memories, consciousness and personality. We know a lot more about the brain than we used to, but it still seems far too complicated for human understanding.

Fortunately, the brain contains many small networks of neurons that carry out some specific function: vision, hearing, movement. It makes sense to tackle these simple modules first. Moreover, we have good mathematical models of nerve cell behaviour. In 1952, Alan Hodgkin and Andrew Huxley wrote down the “Hodgkin-Huxley equations” for the transmission of a nerve impulse, which won them the 1963 Nobel Prize in Medicine. We also have effective techniques for understanding small networks’ components and how they are linked.

Many of these simple networks occur in the visual system. We used to think that the eye was like a camera, taking a “snapshot” of the outside world that was stored in the brain like a photo stuck in an album. It uses a lens to focus an image on to the retina at the back of the eye, which functions a bit like a roll of film – or, in today’s digital cameras, a charge-coupled device, storing an image pixel by pixel. But we now know that when the retina sends information to the brain’s visual cortex, the similarity to a camera ends.

Although we get a strong impression that what we are seeing is “out there” in front of us, what determines that perception resides inside our own heads. The brain decomposes images into simple pieces, works out what they are, “labels” them with that information, and reassembles them. When we see three sheep and two pigs in a field, we “know” which bits are sheep, which are pigs, and how many of each there are. If you try to program a computer to do that, you quickly realise how tricky the process is. Only very recently have computers been able to distinguish between faces, let alone sheep and pigs.

Probing the brain’s detailed activity is difficult. Rapid progress is being made, but it still takes a huge effort to get reliable information. But when science cannot observe something directly, it infers it, working indirectly. An effective way to infer how something functions is to see what it does when it goes wrong. It may be hard to understand a bridge while it stays up, but you can learn a lot about strength of materials when it collapses.

The visual system can “go wrong” in several interesting ways. Hallucinogenic drugs can change how neurons behave, producing dramatic images such as spinning spirals, which originate not in the eye, but in the brain. Some images even cause the brain to misinterpret what it’s seeing without outside help. We call them optical illusions.

One of the earliest was discovered in Renaissance Italy in the 16th century. Giambattista della Porta was the middle of three surviving sons of a wealthy merchant nobleman who became secretary to the Holy Roman emperor Charles V. The father was an intellectual, and Giambattista grew up in a house in Naples that hosted innumerable mathematicians, scientists, poets and musicians. He became an outstanding polymath, with publications on secret codes (including writing on the inside of eggshells), physiology, botany, agriculture, engineering, and much else. He wrote more than 20 plays.

Della Porta was particularly interested in the science of light. He made definitive improvements to the camera obscura, a device that projects an image of the outside world into a darkened room; he claimed to have invented the telescope before Galileo, and very likely did. His De refractione optices of 1593 contained the first report of a curious optical effect. He arranged two books so that one was visible to one eye only and the other to the other eye. Instead of seeing a combination of the two images, he perceived them alternately. He discovered that he could select either image at will by consciously switching his attention. This phenomenon is known today as binocular rivalry.

Two other distinct but related effects are impossible figures and visual illusions. In rivalry, each image appears unambiguous, but the eyes are shown conflicting images. In the other two phenomena, both eyes see the same image, but in one case it doesn’t make sense, and in the other it makes sense but is ambiguous.

Impossible figures at first sight seem to be entirely normal, but depict things that cannot exist – such as Roger Shepard’s 1990 drawing of an elephant in which everything above the knees makes sense, and everything below the knees makes sense, but the two regions do not fit together correctly. The Dutch artist Maurits Escher made frequent use of this kind of visual quirk.

In 1832, the Swiss crystallographer Louis Necker invented his “Necker cube” illusion, a skeletal cube that seems to switch its orientation repeatedly. An 1892 issue of the humorous German magazine Fliegende Blätter contains a picture with the caption “Which animals are most like each other?” and the answer “Rabbit and duck”. In a 1915 issue of the American magazine Puck, the cartoonist Ely William Hill published “My wife and my mother-in-law”, based on an 1888 German postcard. The image can be seen either as a young lady looking back over her shoulder, or as an elderly woman facing forwards. Several of Salvador Dalí’s paintings include illusions; especially Slave Market With the Apparition of the Invisible Bust of Voltaire, where a number of figures and everyday objects, carefully arranged, combine to give the impression of the French writer’s face.

Illusions offer insights into how the visual system processes images. The first few stages are fairly well understood. The top layer in the visual cortex detects edges of objects and the direction in which they are pointing. This information is passed to lower layers, which detect places where the direction suddenly changes, such as corners. Eventually some region in the cortex detects that you are looking at a human face and that it belongs to Aunt Matilda. Other parts of the brain are alerted, and you belatedly remember that tomorrow is her birthday and hurry off to buy a present.

These things don’t happen by magic. They have a very definite rationale, and that’s where the mathematics comes in. The top layer of the visual cortex contains innumerable tiny stacks of nerve cells. Each stack is like a pile of pancakes, and each pancake is a network of neurons that is sensitive to edges that point in one specific direction: one o’clock, two o’clock and so on.

For simplicity, call this network a cell; it does no harm to think of it as a single neuron. Roughly speaking, the cell at the top of the stack senses edges at the one o’clock position, the next one down corresponds to the two o’clock angle, and so on. If one cell receives a suitable input signal, it “fires”, telling all the other cells in its stack: “I’ve seen a boundary in the five o’clock direction.” However, another cell in the same stack might disagree, claiming the direction is at seven o’clock. How to resolve this conflict?

Neurons are linked by two kinds of connection, excitatory and inhibitory. If a neuron activates an excitatory connection, those at the other end of it are more likely to fire themselves. An inhibitory connection makes them less likely to fire. The cortex uses inhibitory connections to reach a definite decision. When a cell fires, it sends inhibitory signals to all of the other cells in its stack. These signals compete for attention. If the five o’clock signal is stronger than the seven o’clock one, for instance, the seven o’clock one gets shut down. The cells in effect “vote” on which direction they are detecting and the winner takes all.

Many neuroscientists think that something very similar is going on in visual illusions and rivalry. Think of the duck and rabbit with two possible interpretations. Hugh R Wilson, a neuroscientist at the Centre for Vision Research at York University, Toronto, proposed the simplest model, one stack with just two cells. Rodica Curtu, a mathematician at the University of Iowa, John Rinzel, a biomathematician then at the National Institutes of Health, and several other scientists have analysed this model in more detail. The basic idea is that one cell fires if the picture looks like a duck, the other if it resembles a rabbit. Because of the inhibitory connections, the winner should take all. Except that, in this illusion, it doesn’t quite work, because the two choices are equally plausible. That’s what makes it an illusion. So both cells want to fire. But they can’t, because of those inhibitory connections. Yet neither can they both remain quiescent, because the incoming signals encourage them to fire.

One possibility is that random signals coming from elsewhere in the brain might introduce a bias of perception, so that one cell still wins. However, the mathematical model predicts that, even without such bias, the signals in both cells should oscillate from active to inactive and back again, each becoming active when the other is not. It’s as if the network is dithering: the two cells take turns to fire and the network perceives the image as a duck, then as a rabbit, and keeps switching from one to the other. Which is what happens in reality.

Generalising from this observation, Wilson proposed a similar type of network that can model decision-making in the brain – which political party to support, for instance. But now the network consists of several stacks. Maybe one stack represents immigration policy, another unemployment, a third financial regulation, and so on. Each stack consists of cells that “recognise” a distinct policy feature. So the financial regulation stack has cells that recognise state regulation by law, self-regulation by the industry, or free-market economics.

The overall political stance of any given political party is a choice of one cell from each stack – one policy decision on each issue. Each prospective voter has his or her preferences, and these might not match those of any particular party. If these choices are used as inputs to the network, it will identify the party that most closely fits what the voter prefers. That decision can then be passed to other areas of the brain. Some voters may find themselves in a state akin to a visual illusion, vacillating between Labour and Liberal Democrat, or Conservative and Ukip.

This idea is speculative and it is not intended to be a literal description of how we decide whom to vote for. It is a schematic outline of something more complex, involving many regions of the brain. However, it provides a simple and flexible model for decision-making by a neural network, and in particular it shows that simple networks can do the job quite well. Martin Golubitsky of the Mathematical Biosciences Institute at Ohio State University and Casey O Diekman of the University of Michigan wondered whether Wilson’s networks could be used to model more complex examples of rivalry and illusions. Crucially, the resulting models allow specific predictions about experiments that have not yet been performed, making the whole idea scientifically testable.

The first success of this approach helped to explain an experiment that had already been carried out, with puzzling results. When the brain reassembles the separate bits of an image, it is said to “bind” these pieces. Rivalry provides evidence that binding occurs, by making it go wrong. In a rivalry experiment carried out in 2006 by S W Hong and S K Shevell, the subject’s left eye is shown a horizontal grid of grey and pink lines while the right eye sees a vertical grid of grey and green lines. Many subjects perceive an alternation between the images, just as della Porta did with his books. But some see two different images alternating: pink and green vertical lines, and pink and green horizontal lines – images shown to neither eye. This effect is called colour misbinding; it tells us that the reassembly process has matched colour to grid direction incorrectly. It is as if della Porta had ended up seeing another book altogether.

Golubitsky and Diekman studied the simplest Wilson network corresponding to this experiment. It has two stacks: one for colour, one for grid direction. Each stack has two cells. In the “colour” stack one cell detects pink and the other green; in the “orientation” stack one cell detects vertical and the other horizontal. As usual, there are inhibitory connections within each stack to ensure a winner-takes-all decision.

Following Wilson’s general scheme, they also added excitatory connections between cells in distinct stacks, representing the combinations of colour and direction that occur in the two “learned” images – those actually presented to the two eyes. Then they used recent mathematical techniques to list the patterns that arise in such a network. They found two types of oscillatory pattern. One corresponds to alternation between the two learned images. The other corresponds precisely to alternation between the two images seen in colour misbinding.

Colour misbinding is therefore a natural feature of the dynamics of Wilson networks. Although the network is “set up” to detect the two learned images, its structure produces an unexpected side effect: two images that were not learned. The rivalry experiment reveals hints of the brain’s hidden wiring. The same techniques apply to many other experiments, including some that have not yet been performed. They lead to very specific predictions, including more circumstances in which subjects will observe patterns that were not presented to either eye.

Similar models also apply to illusions. However, the excitatory connections cannot be determined by the images shown to the two eyes, because both eyes see the same image. One suggestion is that the connections may be determined by what your visual system already “knows” about real objects.

Take the celebrated moving illusion called “the spinning dancer”. Some observers see the solid silhouette of a dancer spinning anticlockwise, others clockwise. Sometimes, the direction of spin seems to switch suddenly.

We know that the top half of a spinning dancer can spin either clockwise or anticlockwise. Ditto for the bottom half. In principle, if the top half spins one way but the bottom half spins the other way, you would see the same silhouette, as if both were moving together. When people are shown “the spinning dancer”, no one sees the halves moving independently. If the top half spins clockwise, so does the bottom half.

Why do our brains do this? We can model that information using a series of stacks that correspond to different parts of the dancer’s body. The brain’s prior knowledge sets up a set of excitatory connections between all cells that sense clockwise motion, and another set of excitatory connections between all “anticlockwise” cells. We can also add inhibitory connections between the “clockwise” and the “anticlockwise” cells. These connections collectively tell the network that all parts of the object being perceived must spin in the same direction at any instant. Our brains don’t allow for a “half and half” interpretation.

When we analyse this network mathematically, it turns out that the cells switch repeatedly between a state in which all clockwise cells are firing but the anticlockwise ones are quiescent, and a state in which all anticlockwise cells are firing but the clockwise ones are quiescent. The upshot is that we perceive the whole figure of the dancer switching directions. Similar networks provide sensible models for many other illusions, including some in which there are three different inputs.

These models provide a common framework for both rivalry and illusion, and they unify many experiments, explain otherwise puzzling results and make new predictions that can be tested. They also tell us that in principle the brain can carry out some apparently complex tasks using simple networks. (What it does in practice is probably different in detail, but could well follow the same general lines.)

This could help make sense of a real brain, as new experiments improve our ability to observe its “wiring diagram”. It might not be as ambitious as trying to model the whole thing on a computer, but modesty can be a virtue. Since simple networks behave in strange and unexpected ways, what incomprehensible quirks might a complicated network have?

Perhaps Dalí, and Escher, and the spinning dancer can help us find out. 

Ian Stewart is Emeritus Professor of Mathematics and Digital Media Fellow at the University of Warwick

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Happiness is a huge gun: Cold War thrillers and the modern nuclear deterrent

For all that books and films laud Britain's strength, ultimately, they show that our power is interdependent.

Francisco “Pistols” Scaramanga, the ­assassin for hire in Ian Fleming’s 1965 James Bond novel, The Man With the Golden Gun, has invested more than money in his favourite weapon. Bond’s colleagues in the Secret Service have concluded from Freudian analysis that Scaramanga’s golden gun is “a symbol of virility – an extension of the male organ”. It is just one of many phallic weapons in the Bond saga. In Dr No, for instance, Bond reflects on his 15-year “marriage” to his Beretta handgun as he fondly recalls “pumping the cartridges out on to the bedspread in some hotel bedroom somewhere around the world”. Objectively speaking, guns comprise little more than highly engineered metal and springs, but Fleming invests them with an ­extraordinary degree of psychosexual significance.

Size matters in the Bond novels – a point made by a furious Paul Johnson in a review of Dr No for this paper in 1958 (“everything is giant in Dr No – insects, breasts, and gin-and-tonics”). One of the Bond stories’ biggest weapons is a rocket carrying an atomic warhead: the Moonraker, which gives its name to the third Bond novel, published in 1955. The most important thing about the Moonraker is that it is apparently British – a gift to a grateful nation from the plutocrat Sir Hugo Drax. And, like Bond’s Beretta, it is freighted with psychosexual significance. When Bond first lays eyes on it there is no doubt that this is an erotically charged symbol of destructive power. “One of the most beautiful things I’ve ever seen,” Bond says, with a “rapt expression”:

Up through the centre of the shaft, which was about thirty feet wide, soared a pencil of glistening chromium [. . .] nothing marred the silken sheen of the fifty feet of polished chrome steel except the spidery fingers of two light gantries which stood out from the walls and clasped the waist of the rocket between thick pads of foam-rubber.

The guns in the Bond books can be seen as expressions of their bearer’s power – or, as with Scaramanga’s golden gun, compensation for a lack of virility. The Moonraker is equally symbolic, but on a far larger scale: an expression of a nation’s geopolitical power, or compensation for its impotence.

As what is known officially as Britain’s independent nuclear deterrent (“Trident” to everyone else) returns to the top of the political agenda, the cultural dimension of the debate will no doubt continue to be overlooked. Yet culture matters in politics, especially when the issue is a weapon. As the guns in the Bond novels remind us, weapons are not merely tools, they are also symbols. Trident is not just a system comprising nuclear warheads, missiles and four Vanguard-class submarines. Its symbolic meanings are, to a great extent, what this debate is about. Trident stands for Britain itself, and it does so for different people in different ways. Your opinion on whether to cancel or replace it depends to a great extent on what kind of country you think Britain is, or ought to be.

The Cold War British spy thriller is particularly topical because it developed in tandem with Britain’s nuclear programme through the 1950s and 1960s. Moonraker was published just weeks after Churchill’s government announced its intention to build an H-bomb in the 1955 defence white paper, and three years after Britain’s first atomic test on the Montebello Islands, Western Australia. These novels drew on technological reality in their plots concerning the theft of nuclear secrets or the proliferation of nuclear technology, but they influenced reality as well as reflected it, with stories of British power that helped create Britain’s image of itself in a postwar world.

The main theme of the genre is the decline of British power and how the country responded. Atomic or nuclear weapons serve this as symbols and plot devices. Len Deighton’s debut novel, The Ipcress File (1962), for instance, concerns a plan to brainwash British scientists to spy for the Soviet Union, and has as its centrepiece an American neutron-bomb test on a Pacific atoll, observed by a British double agent who is transmitting Allied secrets to an offshore Soviet submarine. The novel’s technical dialogue on nuclear technology, and its appendices providing a fictionalised account of the Soviet Union’s first atomic bomb test and a factual explanation of the neutron bomb, are in the book not merely for verisimilitude: Deighton’s British spies are observers or victims of the nuclear arms race between the US and the USSR, agents with remarkably little agency.

A more dour variation on the theme is John le Carré’s The Looking Glass War (1965), in which the prospect of obtaining information on Soviet nuclear missiles in East Germany provokes “the Department”, a failing military intelligence organisation, to try to regain its wartime glory with an intelligence coup. This hubris leads to tragedy as its amateurish operation unravels to disastrous effect, le Carré’s point being that military and economic might cannot be regained through nostalgic wish-fulfilment. These novels situate British decline in the context of superpower domination; their characters recall the technological and operational successes of the Second World War but seem unable to accept the contemporary reality of military and geopolitical decline. For Deighton and le Carré, Britain simply doesn’t matter as much as it used to, which is why, in le Carré’s later Smiley novels and Deighton’s Game, Set and Match trilogy (1983-85), the spymasters are so desperate to impress the Americans.

Fleming is usually seen as a reactionary, even blimpish writer – his England was “substantially right of centre”, Kingsley Amis remarked – and he signalled his own politics by making a trade unionist the ­villain of his first novel, Casino Royale (1953). So it might seem surprising that he was as concerned as his younger contemporaries Deighton and le Carré with British decline. The historian David Cannadine, for one, emphasises that although Fleming may have been aghast at certain aspects of postwar change such as the welfare state and unionisation (opinions that Bond makes no secret of sharing), he simply refused to believe that Britain was in decline, a refusal embodied in Bond’s very character.

Bond the man is more than the “anonymous, blunt instrument wielded by a ­government department” that Fleming described to the Manchester Guardian in 1958. He is an expression of the British state itself, demonstrating Britain’s toughness while besting its enemies – the Russian agents of SMERSH and, later, the international criminals and terrorists of SPECTRE. He is supported by a formidable apparatus of technological and logistical capability that mythologises British research and development, which had peaked during the Second World War (a point made more obviously in the film franchise when Fleming’s Armourer becomes the white-coated Q, heir to Barnes Wallis and the ingenious technicians of the Special Operations Executive). And, as Cannadine astutely observes, “this comforting, escapist theme of Britain’s continued pre-eminence” is most evident in Bond’s relationship with the United States. The Americans may have more money, but they cannot spy or fight anywhere near as well as Bond, as is made plain when the hapless Felix Leiter, Bond’s friend in the CIA, literally loses an arm and a leg to one of Mr Big’s sharks in Live and Let Die (1954).

Moonraker, however, exposes a more complex and sceptical side to Fleming’s Bond. It is significant that this emerges in a book that is explicitly about Englishness and the Bomb. The rocket is being built atop another symbol: the white cliffs of Dover, prompting some surprisingly lyrical passages on the beauty of South Foreland coast. And yet, though replete with emblems of English tradition and bursting with hatred of ugly, evil-minded foreigners, this novel has an unmistakable political subtext that undermines its apparent confidence in British power. Drax, it turns out, is a patriot – but a patriot of Nazi Germany, which he had served as an SS officer and plans to avenge with a missile that is pointing not, as everyone believes, at a test site in the North Sea, but at central London, the intended Ground Zero being a flat in Ebury Street, Belgravia (the location, incidentally, of Fleming’s own bachelor pad in the 1930s and 1940s). The missile has been designed and built by engineers from Wernher von Braun’s wartime rocket programme, and its atomic warhead has been generously donated by the Soviet Union, which is looking to bring Britain to its knees without having to go through the rigmarole of fighting a war.

The Moonraker, we are told repeatedly, will restore Britain to its rightful place at the global top table after its unfortunate postwar period of retrenchment and austerity. But the rocket is not British, except in being built on British soil, and the aim of the man controlling it is to destroy British power, not project it. The implication is that Britain is not only incapable of looking after its own defences, but also pathetically grateful for the favours bestowed on it. After the missile is fired, its trajectory diverted by Bond back to the original target (thereby fortuitously taking out a Soviet submarine carrying the fleeing Drax), the government decides to cover it all up and allow the public to continue believing that the Moonraker is a genuinely British atomic success.

One of the ironies of the Bond phenomenon is that by examining the myths and realities of British hard power, it became a chief instrument of British soft power. Of the first 18 novels to sell over a million copies in Britain, ten were Bond books, and Moonraker (by no means the most successful instalment of the saga) was approaching the two million mark 20 years after publication. The film franchise continues to offer Cannadine’s “comforting, escapist” image of Britain (the two most recent pictures, directed by Sam Mendes, are especially replete with British icons), but the novels are altogether more uncertain about Britain’s role in the world. Moonraker is full of anxiety that the myth of British power is nothing more than a myth, that Britain lacks the industrial and scientific wherewithal to return to greatness. It even conjures up an image of the apocalypse, reminding readers of the precariousness of those cherished British values and institutions, when the love interest, the improbably named Special Branch detective Gala Brand, imagines the terrible consequences of Drax’s plan:

The crowds in the streets. The Palace. The nursemaids in the park. The birds in the trees. The great bloom of flame a mile wide. And then the mushroom cloud. And nothing left. Nothing. Nothing. Nothing.

***

Even though their plots ensure that apocalypse is averted, Cold War thrillers thus made their own contribution to forcing us to imagine the unimaginable, as did more mainstream post-apocalyptic novels such as William Golding’s Lord of the Flies (1954), Nevil Shute’s bestseller On the Beach (1957) and The Old Men at the Zoo (1961) by Angus Wilson. In Desmond Cory’s Shockwave, first published in 1963 as Hammerhead and featuring the Spanish-British agent Johnny Fedora (whose debut preceded Bond’s by two years), Madrid is saved from destruction by a nuclear bomb that the Soviet master spy Feramontov almost succeeds in delivering to its target. As he contemplates his objective, Feramontov muses that, in the “bomb-haunted world of the Sixties”, death in a nuclear fireball “might even come as a release, like the snapping of an overtautened string; and after the rains of death had flooded the Earth, those who survived in the sodden ruins might think of him as a benefactor of the race”.

But where the post-apocalyptic dystopias might be viewed as an argument for nuclear disarmament, later Cold War thrillers such as Cory’s usually accepted the fact of mutually assured destruction – and that British peace and prosperity were guaranteed by US nuclear firepower. Nowhere is this more apparent than Frederick Forsyth’s 1984 bestseller, The Fourth Protocol, which turns the Labour Party’s famously unilateralist 1983 election manifesto into a uniquely party-political espionage plot. In it, the general secretary of the Soviet Union conspires with the elderly Kim Philby to smuggle into Britain a small, self-assembly nuclear bomb that a KGB “illegal” will put together and ­detonate at a US air force base in East Anglia.

Unlike in Moonraker and Shockwave, however, the objective is not to provoke hostilities or prompt military capitulation, but to persuade the British public to vote Labour – by provoking horror and outrage at the risks of US nuclear weapons remaining on British soil. However, the new and moderate Labour leader, Neil Kinnock, will have a scant few hours in Downing Street, as a hard-left rival under Soviet control (such as a certain Ken Livingstone, whom Philby describes as “a nondescript, instantly forgettable little fellow with a nasal voice”) will at once usurp Kinnock and reinstate a policy of unilateral disarmament, leading to the removal of the US missiles.

The ideological force of Forsyth’s novel is clear enough: Britain is beset by enemies within and without, and must arm itself morally and politically against communism. But although this is an insistently, even tiresomely patriotic novel, its plot makes no attempt to conceal Britain’s relative military weakness and dependence on the United States, though disaster is averted by the combined brilliance of MI5, MI6 and the SAS. The Fourth Protocol thus becomes an allegory of this country’s world-leading “niche capabilities”, which maintain Britain’s prestige and relevance despite its declining military and economic might.

Today, the political argument remains on much the same terms as at the start of the Cold War. Whichever way you look at it, Trident symbolises Britain. To its supporters, it is symbolic of Britain’s talent for “punching above its weight”, and its responsibility to protect freedom and keep the global peace. To its opponents, it is an emblem of economic folly, militaristic excess, and a misunderstanding of contemporary strategic threats; it is an expression not of British confidence but of a misplaced machismo, a way for Britons to feel good about themselves that fails to address the real threats to the nation. One academic, Nick Ritchie of York University, argues that Britain’s nuclear policy discourse “is underpinned by powerful ideas about masculinity in international politics in which nuclear weapons are associated with ideas of virility, strength, autonomy and rationality”.

In 1945, shortly after Hiroshima became a byword for mass destruction, George ­Orwell predicted in his essay “You and the Atom Bomb” that nuclear weapons would bring about what he was the first to call a “cold war”. Because an atomic bomb “is a rare and costly object as difficult to produce as a battleship”, it could be produced at scale only by countries with vast industrial capacity; this would lead to the emergence of two or three superpowers, confronting each other in a “peace that is no peace”.

Orwell’s point about industrial capacity helps explain why Trident is totemic: it is proof that our industrial might has not entirely vanished. Alternatively, it can be seen as a consolation for industrial decline. This may be why the huge cost of the Successor programme – one of the main arguments wielded by Trident’s opponents against replacement – appears to be a source of pride for the government: the Strategic Defence and Security Review proclaims that, at £31bn, with a further £10bn for contingencies, Successor will be “one of the largest government investment programmes”.

Clearly, size matters today as much as it did when Fleming was writing. But Moonraker again helps us see that all is not what it seems. Just as the Moonraker is a German missile with a Soviet warhead, even if it is being built in Kent, so the missiles carried by the Vanguard-class submarines are, in fact, made in California, Britain having given up missile production in the 1960s. The Trident warheads are made in Berkshire – but by a privatised government agency part-owned by two American firms. Trident may be British, but only in the way Manchester United or a James Bond movie are British.

The Cold War spy thriller presciently suggests that true independence is an illusion. Britain may consume the most destructive weapons yet invented, but it can no longer produce them or deliver them without America’s industrial might. British power is interdependent, not independent: that is the Cold War thriller’s most politically prescient message.

Andrew Glazzard is a senior research fellow at the Royal United Services Institute and the author of “Conrad’s Popular Fictions: Secret Histories and Sensational Novels” (Palgrave Macmillan)

This article first appeared in the 21 July 2016 issue of the New Statesman, The English Revolt