Pro and anti EU campaigners put on a show of their own outside Parliament as TV crews from around the world gathered for the Brexit vote.
College Green was a cacophony of noise and a sea of colour as banner-waving protesters went head-to-head.
The crowds swelled as the day wore on and the chanting got louder as the two factions tried to drown each other out.
Hundreds of people, bedecked in EU and Union flags and a variety of fancy dress, took the chanting to a crescendo above the passing traffic before Theresa May’s moment of truth in the House of Commons.
But there was no repeat of last week’s ugly scenes when a Brexit-backing crowd surrounded Remain-supporting Tory MP Anna Soubry and accused her of being a Nazi.
Tensions rose slightly when Brexiteers dressed in the yellow vests some have adopted indulged in a bit of flag burning.
But the jostling that followed involved TV crews and photographers eager for shots of the policeman dispatched to deal with the small fire.
The animated crowds vied for position with an array of tents housing the world’s media, eager to chart some of the most important moments in the UK’s modern history.
Security stewards estimated around 90 national and international media outlets were represented.
A stream of MPs including Brexiteer Jacob Rees-Mogg and Remainer Hilary Benn passed the crowds as they arrived for TV interviews.
Mr Rees-Mogg was jeered by Remain supporters crowded outside the media enclosure as he told reporters “fear mongering” about a no-deal Brexit was “fundamentally flawed”.
One man dressed as Boris Johnson handed out fake “£350 million” banknotes decorated with the former foreign secretary’s face.
And a giant carnival-style float was towed around Parliament with an effigy of a Brexit “monstrosity” with the heads of Theresa May, Boris Johnson, Michael Gove and David Davis.
Other banners carried the messages “Leave Means Leave” and “No Deal No Problem”.
As the hour of the crucial vote loomed, the excitable crowd looked to be one of the biggest seen outside the Commons in the weeks leading up to Mrs May’s D-Day.
Police mounted extra patrols but the atmosphere remained mostly peaceful and “polite”, according to campaigners on both sides.
A Scotland Yard spokeswoman said she was “not aware” of any arrests.
Roy Motteram, 62, a remain campaigner from Thame, Oxfordshire, said the atmosphere remained friendly despite the clash of views.
He said: “We chatted quite normally with people on both sides. It was polite.”
Paul Clarke, 56, from Suffolk, who carried a “Leave Means Leave” placard, added: “It has been generally good. There are a couple of people who are a bit rowdy but aside from that it’s all very good-natured.”
The demonstrations also became a spectacle for tourists as many stopped to photograph the banners and costume-clad activists.
Vladimir Kugel, 38, a tourist from Israel visiting London with his wife, said: “I didn’t expect this. It’s our first time in London and it’s interesting from the point of seeing how people say what they want and express their opinions.
“It’s an experience. I hope the majority will be satisfied by the result.”