One Anonymous protester told of how he was moved to join the group after being arrested under the Computer Misuse Act, despite having "done nothing wrong".
Sean Roesner, 21, a self-employed computer programmer, travelled to tonight's protest with his brother and friend from King's Lynn, Norfolk this afternoon.
He said: "We turned up and the protest was at Buckingham Palace. When we arrived people were firing fireworks at the Palace.
"It was funny. I didn't have any but I would have fired some if I had.
"I joined Anonymous because I was arrested under the Computer Misuse Act. I spent eight months on police bail last year and had done nothing wrong."We are here to stand up for what we believe in, to make the world a better place."
Mr Roesner said his friend had been among a group of people encircled by the police on The Mall and was waiting for him to be released so they could return home.
More top news
Royal Navy vessels are following Russian warships 'every inch of the way' as they pass through the English Channel on their way to Syria.
Official figures show parents are increasingly defying government rules and taking their children on unauthorised trips during term-time.
Tabloid 'King of the Sting' given a jail sentence for tampering with evidence in the collapsed drugs trial of pop star Tulisa Contostavlos.