Thousands of anti-Brexit demonstrators marched to Westminster - before Theresa May officially triggers the UK's divorce from Europe on Wednesday.
Marchers showed defiance as they waved their banners during the peaceful protest just days after knife-wielding terrorist Khalid Masood attacked the heart of British democracy.
Opening the event, Alastair Campbell said: "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."
Campaigners stood with their heads bowed for a minute-long silence to remember the victims, with the only sound the chiming of Big Ben.
Liberal Democrat leader Tim Farron addressed the crowd, insisting "democracy continues" and adding: "We stand in defiance of that attack."
Organisers refused to call off the event after the attack earlier this week, saying 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."
It came as European Union leaders agreed that member states should be allowed to pursue integration at different paces.
The 27 other EU leaders were marking the union's 60th anniversary at an informal summit in Rome without the Prime Minister.
Here is a round-up of the best pictures from the day: