Brits living in Malaga and Granada provinces were among those who travelled to London from all corners of Europe and the UK for last Saturday's People's Vote march.
The march was organised by The People's Vote campaign group which wants the government to hold a referendum on the final Brexit deal.
While no official statistics have been released, estimates range from 700,000 people to one million attending the event.
Pat Laing, who lives in Malaga, flew back to the UK especially for the march. She said, "I went because not a day has gone by since the June 2016 referendum when I haven't been furious about the whole Brexit referendum campaign."
She added that "the arrogant complacency of the Remain campaign, the lies, manipulation and the illegal funding of the Leave campaign, the effects of 40 years of negative narrative about the EU that the UK population have been fed, but most of all the risk to peace and harmony in Ireland that Brexit represents" all compelled her to be at what could well be the final protest of its kind before the UK leaves the EU, on 29 March next year.
Biggest anti-Brexit rally
Malcom Perry who lives in Montefrio in Granada province, said, "I have been at three Stop Brexit and People's Vote marches and this by far was the best in terms of attendance. I was absolutely astounded by the sheer numbers. I don't think anyone expected quite so many people."
The march started at midday in Park Lane in the centre of London and ended at Parliament Square where speeches were given by the mayor of London, Sadiq Khan, who led the march; Liberal Democrat leader, Vince Cable; and comedian Steve Coogan, who is best known for his radio presenter character, Alan Partidge. Coogan even paid for coaches to bring supporters from UK towns.
SNP leader, Nicola Sturgeon, sent a video message of support which was aired as part of the speeches, saying that her party "would support a vote that would give the option of staying in the EU".
Several people, including Malcom Perry and John Moffett, who travelled back from La Herradura for the event, commented that they "missed the speeches" as they "didn't arrive in Parliament Square in time due to the sheer numbers of people".
Future of young people
One of the clear messages coming from the march was the importance of young people and how they would be affected by Brexit. A number of young people attended the march, with banners demonstrating that they were too young to vote in the referendum but would be old enough to vote in a People's Vote.
Pat Laing, who met up with the grandchildren of a school friend in London, said that Brexit would "affect the future prospects of young people". Alastair Stewart, an advisor to the Bremain in Spainorgansiation, said, "It's madness and slander to think of British migrants in Europe as exclusively retirees or backpackers. Our backgrounds and circumstances are vastly diverse, rising far above the cliché of 'expats in the sun'. We find that cliché quite offensive."
Meanwhile, Former UKIP leader and hard Brexiteer, Nigel Farage, held a pro-Brexit rally in Harrogate, North Yorkshire, on the same day, which 1,200 people attended. Farage drew criticism for holding his event in a place which "voted to remain".
British prime minister Theresa May has ruled out a second referendum despite mounting pressure from MPs including those within her Conservative party, as the deadline for an agreement with the EU approaches.
Earlier this week May stated that the deal was "95 per cent done" with the issue of the Irish border the main sticking point. However, on Wednesday, the European Parliament's spokesperson on Brexit, Guy Verhofstadt, said it was "0 per cent done" for MEPs.