Carol singers are to become the latest group to defy a ban on unauthorised protests around Parliament.
The group will test the limits of the new Serious Organised Crime and Police Act by singing in Parliament Square from 1800 GMT on Wednesday.
The law makes demonstrating without police permission an arrestable offence near Parliament.
Singers include long-term anti-war protester Brian Haw and Maya Evans – the first protester to be convicted.
Ironically Mr Haw is the one protester exempt from the ban, due to a Home Office drafting error.
He successfully argued in the High Court that as his four-year vigil pre-dated the law, he did not have to apply for authorisation to continue.
Since the law came into force in August, several people have been arrested and other protesters have been warned off.
Peace campaigner Ms Evans was the first to be convicted under the Act, after reading out the names of soldiers killed in Iraq at the Cenotaph.
Mr Haw will lead the Lord’s Prayer at the service on Wednesday, joined by others including former British ambassador to Uzbekistan, Craig Murray, and a 7 July bombings survivor.
A spokesman for the carol singers, Tim Ireland, said: “In this instance, the police have not been notified. They’ve been invited, certainly, but they have not been notified.
“We believe that the public has the right to gather in a public place and sing Christmas carols. The police may see things differently, we shall see.”
A Scotland Yard spokeswoman was not able to comment on whether a carol service constituted a demonstration and said a decision about whether to take action would be taken on the day.
Hundreds of people will today risk arrest and prosecution by singing Christmas Carols in Parliament Square.
The service will be supported by Maya Anne Evans, recently prosecuted for reading out the names of dead British soldiers near the Cenotaph, together with the former British Ambassador to Uzbekistan Craig Murray, who was forced out of his job for criticising the use of torture, and Rachel North, a survivor of the July 7th bombings.
Writing on her blog, Rachel North says:
“I have been more or less unable to deal with Christmas this year… All the sentiments of peace on earth, hope, joy, when it felt like we were reaching the end of a year of horrible bloodshed and hate and death and war, led by men who claim to be godly, but know so little of compassion, of peace… That both fighting sides say they do it for ‘God’ and ‘freedom’ and ‘justice’ as they murder and main is more than I can stand…
I urge you to join us if you can make it, in Parliament Square on Wednesday this week at 6pm. It’s important to protect these traditions, beloved of us all in this country for a thousand years. Now more than ever.”