Brexit became official Friday at 11 p.m. in London and midnight in Brussels, where the EU is headquartered.
About 200-300 pro-European Union supporters were mocked by pro-Brexit supporters as they walked from Downing Street to the office of the European Commission in London. Police formed a line to keep the two groups apart.
Britain's Queen Elizabeth has approved Prime Minister Boris Johnson's plan to suspend parliament, a statement from the official body of advisers to the Queen, known as the Privy Council, said on Wednesday.
In London, participants heard speeches from opposition politicians on a stage erected on Whitehall before marching through Westminster. Some held hand-written signs reading “defend democracy: resist the parliament shutdown” and “wake up UK! Or welcome to Germany 1933.”
Britain’s opposition Labour Party held on to the parliamentary seat of Peterborough in eastern England on Friday, seeing off a challenge from Nigel Farage’s insurgent Brexit Party.
Britain's government on Wednesday faced a backlash over its new post-Brexit immigration plans, which are designed to cut "cheap labour from Europe" in favour of high-skilled English speakers and boosting the homegrown workforce.
Brexit Secretary Stephen Barclay reiterated that the ideas formally submitted to Brussels this week were "a broad landing zone" to be discussed during "intense negotiations in the coming days."
Accusing the committee of mounting a "political hit job," Johnson said in a statement: "I am being forced out by a tiny handful of people, with no evidence to back up their assertions."