In the long winter that froze the early months of 1963 - one of the coldest of the 20th century - a few people were fanning flames of rebellion. They were peace activists - and anarchists and socialists - who wanted to challenge the power of the military state but to go beyond yet another mass march or yet another sit-down. They had heard through various contacts about a secret government bunker that was supposed to lie somewhere off the A4 near Reading. They set off in search of it in February 1963.
They drove for hours over ice-covered roads, and tramped over snow-covered fields. At the east end of a village called Warren Row, they found a fenced-off hill with a padlocked wooden gate, and an unmarked hut. They climbed over the gate to find a brick boiler house and a wide concrete ramp leading into the hillside. Radio aerials stood a little way off, their cables leading into the hill. One of the explorers tried the doors of the boiler house and found them unlocked. The four of them went in.
Inside, they tried another door on what looked like a cupboard. This was also unlocked, and swung open to reveal a steep staircase leading into an underground office complex. They ran down the stairs, their feet clattering in the silence, and snatched what papers they could from the desks. Then they rushed out and drove away, hardly able to believe their luck.
They had walked straight into a secret government headquarters, called the Regional Seat of Government No 6. It was to be one of the biggest stories of the Sixties and, along with the Profumo affair and other events, would change people's perceptions of how their rulers might behave and how far they could be trusted. At the time, the British public, incredible as it now seems, was being told that a nuclear war, though it meant heavy casualties, would not necessarily be catastrophic. People were kept entirely in the dark about their own government's faith in the possibility of surviving such a war, and about its plans for the well-being not of the ordinary people but of a political elite.
The trespassers called themselves the Spies for Peace - a sort of joke, one of them said later, after such groups as Doctors for Peace and Musicians for Peace. They were young, and they knew they risked long prison sentences. Even 40 years after the event, fearing that they could still be open to prosecution for criminal conspiracy, they wish to remain anonymous. But I believe that, in a new age of protest, we can still learn from them. I have spoken to some of them; one was my late father, Nicolas Walter.
On a second visit, in the small hours of a cold Sunday morning, four Spies for Peace (not exactly the same group) found the boiler house door locked and picked it. This time, they spent several hours there. One took photographs. One copied documents. One traced maps. One went through every drawer and every cabinet. Then they left with a suitcase full of copied papers and a camera full of photographs.
The group typed and duplicated 3,000 leaflets explaining what they had found. Secrecy was paramount. "I was terribly panicky," one ex-spy told me. He paused. "But that was also because I was smoking so much cannabis."
They stuffed envelopes in the night, posted them from all over London, burnt all their own documents, posted the original photographs anonymously to sympathisers, and threw the typewriter they had used into a river. "We wore gloves the whole time," another ex-spy said. "Luckily, it was still so cold, no one wondered about me going into the post office and picking up all these stamps, wearing my gloves."
The effect was explosive. The leaflets were posted to newspapers and to the houses of celebrities, MPs and protesters. Although the government had slapped a D-notice (an advance censorship warning) on any disclosure of the Regional Seats of Government (RSGs), the leaflet, with its cover showing Warren Row and the title "Danger - Official Secret", proved irresistible to the press. On the Saturday of an Easter weekend - when the unilateral nuclear disarmers' now customary march from Aldermaston took place - the story was splashed over every national paper. "We thought the press might ignore it - that they would be in cahoots with the government," said one of the spies. "The headlines, the splashes, the fury - we hadn't counted on that. I remember sitting there with Nicolas [on the train to Aldermaston], reading the front pages, prodding each other in the ribs, feeling just high."
Thousands of protesters immediately went to demonstrate at Warren Row. It was my mother's 21st birthday. Ruth Walter sat with my father, drinking cheap red wine in the thin spring sunshine, singing "We Shall Overcome" with the rest of the crowd. "It was," she recalled, "the most magical day."
Most people seemed to believe that only an insider could have leaked such sensitive and unsettling information. The Sunday Telegraph wrote: "It would be surprising if investigation does not bring to light a shrewd political mind directing this brilliant subversive operation." Later, it referred to "a mastermind behind the Spies for Peace", who was thought to be "a brilliant man who may be doing an important job".
The real spies were known protesters. Most were raided by the Special Branch, and most were questioned, but none was ever charged. "We had been so careful," said one spy. "When I went down for questioning, and they said, would you like a glass of water, sir, I said, yes, quite happily, because I didn't care if they got my fingerprints. There was nothing there to match them against."
To this day, they keep their secrets. "I don't see the point of coming out now," one said. "It was so perfect in its own time. It still makes me laugh. I can't tell you how many people have said to me over the years, oh, when I was in the Spies for Peace, and of course I know bloody well they had nothing to do with it."
At the end of 1963, an official report on civil defence gave information to the public for the first time about the RSGs, and the complicated regional civil defence system was gradually dismantled. But the Spies for Peace story had a greater effect on public attitudes than on government behaviour.
Although it had long been common knowledge among the elite that there was a secret system for wartime government survival, it came as a shock to ordinary people that their rulers were making detailed plans to fight a nuclear war and to ensure the survival only of the politicians and civil servants, without any democratic consent. The story helped to break down the deference that then characterised the British people's relationship with government.
"We were just coming out of the Fifties," says one ex-spy. "In many ways Britain was still trilby hats and brown raincoats. And then this happened. It helped to create the political culture that was the Sixties." "In many ways we were surprised by the effect," says another, "because if people stopped to think, they did know that there would be this system for the survival of the government. But the idea that people had to spy on their own government to get the truth out - this was a very fertile idea, the idea that it was right to ask questions, to battle them for the truth."
The sense of scepticism, the belief that people should pursue their own government and ignore the laws of official secrecy if it seemed to be covering up harmful behaviour - this was the idea that the Spies for Peace helped to advertise.
Writers and journalists began to unearth more about the civil defence system. Peter Laurie wrote about the emergency government system in the Sunday Times in 1967, and then expanded it into a book, Beneath the City Streets (1970). Duncan Campbell, the New Statesman writer, was among those who then took up the baton. These journalists ensured that British people began to take for granted that the need for government secrecy should always be questioned.
But what did the episode mean for the spies themselves? What did they hope to achieve? My father, as well as being an anti-war activist, had long been a committed anarchist. The term now is used mainly of kids who slope along on demonstrations with no particular ideas except to cause as much chaos as possible. But for people such as Nicolas Walter, anarchism was and is a pragmatic political philosophy. Six years after the Spies for Peace broke into RSG-6, Walter published About Anarchism, which became a popular work, translated into many languages across the world. He explained that anarchism has a very straightforward central demand - the removal of authority.
Anarchists, he wrote, believe that a society without government would not lead to chaos, but to a society better than the one we live in now. Anarchism, he said, yokes together the demand for freedom, made by liberals, and the demand for equality, made by socialists: it was possible for a society to run smoothly without authority, with economic organisation based on co-operation, and welfare based on mutual aid. It is a philosophy with a long tradition and many sympathisers, of whom the policeman Brian Paddick - who admitted in an internet chatroom that he found anarchism "attractive" - is only the latest.
In his book, my father explained the dreams, but also grappled with the reality of anarchism. Permanent protest, he admitted, often seemed to be all that anarchism could achieve. "According to this view, there is no hope of destroying the state system, and of putting anarchism into practice . . . so what is important is not the future, but the present, the recognition of a bitter reality and the constant resistance to an ugly situation."
Walter himself suggested that this was a pessimistic view, as might those today who call themselves anarchists - or who hold recognisably anarchist ideas but prefer to use the label anti-capitalist, or no label at all. Many of them may have taken on the classic anarchist vision, that a society without profit or authority would be better than the society we have today. But can they hope for anything other than permanent protest?
Groups such as the Spies for Peace show how protest can achieve change. The current movement for global equality is not an exact parallel to the British peace movement of the Fifties and Sixties: the latter directed its challenges at the state, the contemporary movement mainly at corporations. My father and his friends discovered and published what their government was doing and asked: is that what people want done in their name? Today's protesters unearth the corporations' activities: the facts on sweatshop labour, the effects of the oil companies on indigenous peoples, the environmental problems of GM technology, and so on. Is this, they ask, what consumers want done with their money?
Now, as then, protest counters an idea that is almost universally accepted in our society: that somebody knows better than you do how your life, or your work, or your neighbourhood, should be run. Activists remind us that power is constantly being sucked away from ordinary people, towards the state or the corporation. And they try to remind us that this need not be the only way to organise society - that we could imagine individuals having and exercising more power, and that this sharing of power might create a more open and more equal society.
The Spies for Peace suggested the possibility of people winning power back from the state by breaking into a government bunker on a cold winter night. Activists today who suggest the possibility of winning power back from corporations do it by all sorts of other methods right across the world, from reclaiming the streets for a day to breaking into shareholders' meetings and lying down in front of a bulldozer building a dam. Permanent protest may indeed be the state that activists will always find themselves in, but you could also say, as my father once did: "No one can tell when protest might become effective and the present might suddenly turn into the future."
About Anarchism, by Nicolas Walter, with a new introduction by Natasha Walter, is published this month by Freedom Press (020 7247 9249) priced £3.50