A 44-year-old man was arrested today after trying to enter Buckingham Palace while in possession of a knife, Scotland Yard said.
He was held at around 11.30am when he attempted to get through the north centre gate and was stopped by police.
He was arrested on suspicion of trespassing on a protected site and possession of an offensive weapon and is in custody.
Buckingham Palace said that the Queen was not in the building when the man tried to get in, but would make no further comment.
This latest incident follows a similar situation last month when an intruder was able to scale a fence and get inside the palace, before being arrested by police.
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A few days later Prince Andrew, the Duke of York was ordered to verify his identity by two officers who has failed to recognise him.
He later said he was "grateful" for an apology from the officers who challenged him in the gardens of Buckingham Palace.
In a statement on Sunday he said: "The police have a difficult job to do balancing security for the Royal Family and deterring intruders, and sometimes they get it wrong.
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