Tens of thousands of anti-Brexit demonstrators fell silent at Parliament Square in tribute to the victims of the Westminster attack this afternoon.

Eastern Daily Press: A placard at the anti-Brexit march in London on March 23. Photo: Graham HopkinsA placard at the anti-Brexit march in London on March 23. Photo: Graham Hopkins (Image: Archant)

Around 100 protestors from Norwich and Norfolk set off early this morning to march on Westminster just days before Article 50 - the official process for leaving the European Union - is triggered.

Unite for Europe campaigners marched through central London to Westminster, the scene of floral tributes to those killed and injured in Wednesday's atrocity.

Peter Gallon, from near Mundesley, helped organise the coaches from Norwich and said he was 'flabbergasted' by the numbers.

'I had never been on a march before in my life, but it was the whole Brexit business that made me think; if I go on one this has to be it. A lot of other people obviously felt the same way.

Eastern Daily Press: A placard at the anti-Brexit march on Westminster on March 23. Photo: Ellen Sweet-EscottA placard at the anti-Brexit march on Westminster on March 23. Photo: Ellen Sweet-Escott (Image: Archant)

'With the imminence of the Article 50 declaration being triggered and it being the 60th anniversary of the Treaty of Rome, it just felt right. I think people are starting to realise that things are already beginning to go wrong and we have not even left the EU yet.'

Mr Gallon added everyone on the march had been 'very positive' despite the events of Wednesday afternoon. 'There were lots of police there and marchers had been laying daffodils as they walked past,' he said. 'Everyone was acknowledging the awfulness of what happened, and I think it made them more determined that in a democracy you have to express your right to protest.'

Liberal Democrat leader Tim Farron addressed the crowd, insisting 'democracy continues' and adding: 'We stand in defiance of that attack.'

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.

Eastern Daily Press: A placard at the anti-Brexit march on Westminster on March 23. Photo: Ellen Sweet-EscottA placard at the anti-Brexit march on Westminster on March 23. Photo: Ellen Sweet-Escott (Image: Archant)

Organisers refused to call off the event after the attack earlier in the 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.

The march coincides with the EU's 60th anniversary celebrations in Rome, where leaders of the other 27 members states will gather to discuss plans for the future of the union without the UK.