A man scaled a wall and got into the grounds of Buckingham Palace before being arrested, London police said Thursday.
The 41-year-old man was detained in the palace grounds Wednesday evening on suspicion of trespassing on a protected site, the Metropolitan Police force said.
He was arrested just before 9 p.m., seven minutes after his presence was detected, police said.
The force said the man wasn't armed and was arrested without the use of stun guns. He was being held in custody Thursday.
Commander Adrian Usher, head of the force's royalty protection squad, said that "our security measures worked effectively on this occasion and at no time was any individual at risk."
The palace declined to comment on security, calling it a police matter.
The queen was at the palace Wednesday after attending the State Opening of Parliament.
Several intruders have breached security at the queen's London residence over the years — including a naked paraglider who landed on the roof in 1994.
In 2013, two men were arrested on suspicion of burglary — one in the grounds and one inside an area of the palace that's open to the public during the day.
In 1982, an unemployed man named Michael Fagan managed to sneak into the queen's private chambers while she was still in bed. Elizabeth spent 10 minutes chatting with the intruder before calling for help when he asked for a cigarette.