A fathers' rights campaigner evaded tight security Monday to protest on the balcony at Buckingham Palace, a spokeswoman for Queen Elizabeth said.
"There is a protester on the balcony," the spokeswoman said. "It is a matter for the police."
A spokesman for pressure group Fathers 4 Justice said campaigner Jason Hatch climbed onto the balcony dressed as Batman.
It was the latest in a long line of stunts by the group, who say Britain's courts are biased against fathers in divorce case child access arrangements.
In the most high-profile incident, protesters pelted Prime Minister Tony Blair with flour-filled condoms as he was speaking in parliament in May, informs Reuters.
According to The Mirror the Queen was not in residence as she is at Balmoral in Scotland enjoying her summer break. No other members of the royal family were in residence.
Hatch was stood on a narrow ledge to the right hand side of the main balcony at the front of the palace.
Watched by tourists he unfurled a banner which read: "Super dads of fathers 4 justice". The banner included the word: "Fighting for your right to your kids".
Police were on the scene and appeared to be talking to Hatch. They also cordoned off the area immediately in front of the palace.
One eyewitness said she saw the man dressed as Batman climb up the building at the far right end of the palace and make his way across the front of the building.
A Buckingham Palace spokesman confirmed that the Queen was away at Balmoral on her summer break and that no members of the royal family were in residence.
He said: "There's man there, but it's a police matter. I'm not sure where he is but I can hear him shouting."
On Saturday, a Fathers 4 Justice campaigner brought the London Eye to a standstill after climbing to the top dressed as Spider-Man.
The case of two protesters is being heard at a magistrate's court after they allegedly hurled condoms filled with purple flour at Tony Blair during Prime Minister's Questions, informs Telegraph.