Thirty-eight anti-war demonstrators have been arrested following clashes with police outside Parliament.
Demonstrators were heavily outnumbered by police officers
One man carrying a camera, not thought to be part of the protest, was hurt as officers attempted to contain scuffles.
Organisers had planned to prevent MPs and peers from entering the Palace of Westminster on their first day back from the summer recess.
But those taking part in the "Sack Parliament" demonstration were outnumbered by 800 police on standby.
A small group of protesters, wearing hooded tops and scarves, tried to cross the road from Parliament Square but were prevented from doing so and held in a cordon.
One man was injured in the melee and was treated by paramedics at the scene.
Scotland Yard said the arrests had been for offences including breaching the legislation around demonstrations in Westminster and breach of the peace.
There were thought to be no more than 60 or 70 protesters at the unofficial demonstration's height.
One person was arrested on the way to the demonstration for possession of an offensive weapon and another for possession of drugs.
Lee Dickinson, 24, a carpenter from Sudbury in Suffolk, said: "We are not allowed to do that because of the unbelievable amount of police officers that are here.
"They are our representatives in government but we are not allowed to go near them if we disagree with them."
Another protester, who did not wish to be named, said of the police presence: "I personally think it is a bit depressing, bullying behaviour.
"We have people here to protest peacefully and try and bring a bit of democracy to this country."
The Sack Parliament group says MPs and peers have failed to challenge acts of state terror" around the world and "helped erode our civil rights".
Opposition parties have offered the government a "veil of legitimacy" for its actions, organisers add.