The Mayor of London has begun legal action to remove peace protesters camping in Parliament Square.
Over the past weeks tents and flags have transformed the green into what protesters call Democracy Village.
They include anti-war protester Brian Haw who has previously won legal battles to be allowed to continue his demonstration outside Parliament.
Trespass proceedings brought by Boris Johnson got under way at the High Court on Thursday afternoon.
In addition to the three people named in the Mayor's action, some 15 protesters in court asked to be recognised as defendants.
Their names were taken by the judge and 10 copies of the court documents will be attached to stakes in Parliament Square.
David Forsdick, representing the mayor, said: "The right to protest is highly important and not to be lightly interfered with.
"This is not a case about restricting the right of protest.
"It is about preventing a small group of individuals from unlawfully establishing a tented village and taking possession of an important open space to the exclusion of others."
The case was adjourned until Monday.
In 2007 it was made illegal to hold an unauthorised protest within a square mile of Parliament.
A spokesman for the mayor said previously: "Parliament Square is a world heritage site and top tourist attraction that is visited by thousands of people and broadcast around the world each day.
"The mayor respects the right to demonstrate, however the scale and impact of the protest is now doing considerable damage to the square and preventing its peaceful use by other Londoners, including those who may wish to have an authorised protest."
One protester, Chris Knight, said before the hearing: "I think it is an absolute scandal, it's a disgrace.
"He [Boris Johnson] should be supporting democracy, not opposing it.
"If Boris wins this case it means freedom of speech, freedom of assembly will be put in the dustbin.
"I'd rather he was put in the dustbin."
The move has been welcomed by Westminster City Council whose leader, Councillor Colin Barrow, has accused the protesters of "hijacking" the square.