Early on Saturday morning two brothers scaled the cliff face of Big Ben with a Greenpeace banner reading “Time for Truth” and stayed there for seven hours. Their feat got the day’s protests onto the front pages and hammered home the truth that’s been tormenting Londoners since the Madrid train bombings: no amount of security can guarantee our safety from a terrorist attack and, as the media remind us every day, London may well be next.

The shadow of Madrid hung over the marchers in more ways than one. In spitting rain and gusts of wind that threatened to tug the banners from their hands, thousands (police estimate: 25,000, organizers’ estimate: 100,000) gathered once again in Trafalgar Square under the slogan “No More Lies,” to reiterate their opposition to the war and to commemorate the dead of Iraq and Spain with a flight of black balloons. Everyone I spoke to believed that Blair’s Iraq adventure was a dangerous diversion from the struggle against terror and has put us at greater risk. But apart from the odd placard reading “Aznar down, Blair next,” neither that insight nor Britain’s foreboding has yet found much expression in the theater of protest. A year on, in spite of having been proved right about so much, the movement finds itself at an uncertain turning point.

Inevitably this year’s crowd was more hardcore than before; both the creative and the callow stood out from the mass of “ordinary people.” A group from Birmingham wore Guantanamo-style orange boiler suits to call for the release of British citizen Moazzem Begg; a British offshoot of the American group Codepink protested mines and cluster bombs with Day-Glo feather dusters. Red flags and close-typed hand-outs proclaimed the joy of sects and imminent world revolution. But the union banners were still there, with fewer people under them; the families and CND veterans marched on, although depleted. A London teacher explained how hard it’s been to address students’ disappointment that their voices have been ignored: “For a lot of young people it’s been quite a bitter lesson but I think the movement’s going to go on because of that.”

The problem is, go where? In Spain and in America the war was launched by governments of the right, easy to rally against. But in Labour Britain there’s a far deeper sense of pessimism and betrayal. One man’s handwritten placard read, “Get rid of Blair. Brown wouldn’t have lied to you.” Asked if he really thought that, he just shook his head.

A group called RESPECT: The Unity Coalition has been founded by Stop the War organizers to fill the vacuum and be the movement’s “political wing”; it’s putting up candidates for the European Parliament and the Greater London Authority, and attracting some support at local meetings. A former Labour councillor from Liverpool who’d left the party over the war was marching under its banner; he said he wanted to be part of a broad movement of environmentalists and peace campaigners as well as socialists. But it’s much too soon to tell where any of this might lead. Mostly Londoners are waiting for the other shoe to drop.