Authorities say a man who climbed over a wall and got into the grounds of Buckingham Palace while Queen Elizabeth II was at home is a convicted murderer.

Dennis Hennessy pleaded guilty to trespass at a court appearance Friday.

He was arrested in the palace grounds on Wednesday evening. Police say he was not armed.

Prosecutor Tom Nicholson told the court that 41-year-old Hennessy walked around the gardens for about 10 minutes toward the palace before being arrested. As he was detained he asked "is Ma'am in?" — the courtesy term used for the queen.

Prosecutors said Hennessy was on parole after being convicted of the murder of a homeless man in 1992.