The mood has been jovial and slightly subdued as people were due to gather in Parliament Square near the scene of this week’s terror attack.
Alastair Campbell, the first speaker at the rally, said before a moments silence: “Before we talk about Brexit, before we call on any of the speakers, we need to recognise that something really bad happened not far from here just the other day.”
As ever, being a British protest, one of the highlights is the wide array of incredibly imaginative signs on display.
Organisers said in a statement: “We will not be intimidated. We will stand in unity and solidarity. We will march on the heart of our democracy and reclaim our streets in honour and respect of those that fell.
“We will be observing a minute of silence and remembrance at the start of the rally. We would encourage all attendees to bring with them some symbol of respect and to act in the appropriate fashion on the day.”
The march coincides with the EU’s 60th anniversary celebrations in Rome, where leaders of the other 27 member states will gather to discuss plans for the future of the union without the UK.
Lib Dem former deputy prime minister Nick Clegg, Labour MP David Lammy and Green co-leader Jonathan Bartley were also among those addressing the crowd.
Liberal Democrat leader Tim Farron addressed the crowd, insisting “democracy continues” and adding: “We stand in defiance of that attack.”
He added: “We are here to show solidarity and respect for those who voted leave. We do not believe they wanted this.
“[Theresa May] does not speak for 52 per cent, she barely speaks for 5 per cent.”