Beneath the rigid gaze of Viscount Alanbrooke, whose statue looks across Whitehall to Downing Street, a dozen English Defence League members face a shouting crowd of anti-fascist protesters. Kevin Carroll, a co-leader of the EDL, steps down towards the crowd and taunts them, arms outstretched, making little come-on-then gestures with his fingers. Dressed in a dark suit, he's smiling. It's the EDL's self-image in miniature: relishing the abuse, pretending to be the underdog, when in fact there are a thousand or so supporters around the corner whose islamophobia is nourished by a steady drip-feed from the right-wing press and the posturing of politicians.
Mouthing silently, Carroll mimics the taunts thrown at him. Racist scum? I'm a racist? You're the racists. It's a common refrain whenever the views or the actions of the EDL are challenged; its ideology sits on that fault line in our culture where islamophobia has flourished. How often we hear the question "how can this be racism? Islam is a religion not a race," even though race is not a scientific category but a discredited 19th century biologist's term, and seemingly ignorant of the racism that has been directed by whites, at whites - Irish, Jewish, eastern European - in this country's not-too distant history.
The trigger for the EDL's mobilisation is clear: the appalling murder of Lee Rigby in Woolwich, and the shock it caused, has breathed new life  into their moribund movement. Since 22 May there has been a surge of interest in the EDL online. Most of this won't translate into physical support, but a demonstration in Newcastle on Saturday drew around 1,500 supporters, and a slightly smaller number have turned up on Downing Street this Bank Holiday Monday. It's been mirrored by a backlash against Muslims: the charity Faith Matters has reported  a spike in violent and verbal abuse; at least ten mosques around the UK have been attacked, some with petrol bombs. In that sense, the many who argue that these two violent extremisms feed off one another are correct. But anti-Islam feeling is shared by more than just those on the far-right: a poll by YouGov, published in the Observer on Sunday , suggested that the percentage of people who believe Islam is a threat to democracy had risen to 34 per cent. It was already at 30 per cent the last time the poll was taken, in November 2012.
The smile disappears from Carroll's face as a group of anti-fascist protesters lift up a metal barrier he thought had been keeping him safe, and rush towards him. Carroll looks scared: it's a moment, an onlooker says to me later, when perhaps a thought flashes through Carroll's mind that this confrontation, this hatred, isn't worth it. He retreats, to the safety of Viscount Alanbrooke - the irony of a far-right extremist, however patriotic he might believe himself to be, sheltering beneath the statue of a Second World War commander, is not lost on some .
It's only a small victory for the anti-fascists - in fact, they are outnumbered by about two to one. Eventually the police will escort the EDL crowd to their rallying point on Whitehall, before allowing them to filter off into the West End. Nevertheless, the EDL remains as unpopular as ever with the general public, even if its supporters have found a new enthusiasm in the past week. Some 84 per cent polled by YouGov said they would "never join" the group - a 7-point increase from last November. Help for Heroes, the charity that provides aid to injured servicemen and women, has rejected donations  from the EDL.
But the EDL's heavy symbolism - the St George's flags, the militarism, the often repeated claim that "there's one law for us and another for them" - and their use of violence and intimidation to elbow their way into the national media finds a resonance well beyond its size. How long before a demagogue like Nigel Farage - whose own party is experienced at playing on islamophobia  when it suits - tells us to vote for him, to do something about Muslims who "won't integrate", in order to keep the EDL at bay? He's already made similar claims with regards to immigration and the BNP. How will mainstream politicians react if the disillusionment echoed by supporters of right-wing populist movements, whether they're street-based or election-focused, continues to deepen? Extremism of this sort is what fills a vacuum: when people feel ignored and that, for whatever reason, they have no political voice.
Later, the EDL's figurehead, "Tommy Robinson", a tanning-shop owner from Luton whose real name is Stephen Lennon, will give a speech to his elated supporters. "They've had their Arab Spring," he says, with only a touch of Alan Partridge about it. "Now let's have an English Spring." It's not particularly original - the French hard right have used something similar during their recent protests against gay marriage - but it's strikingly ambiguous. The Arab Spring, after all, was an uprising of people whose democratic rights had been denied. Could that at all be true in Britain? It's an urgent question. Without a doubt, though, the EDL is the wrong answer.