He didn't get inside the palace. He didn't get close to the queen. She wasn't even home.
But a 44-year-old man with a knife did try to enter the Buckingham Palace just before noon today. Police arrested him as he attempted to dart through a palace gate.
They found the knife when they searched him. He is now in custody.
It was the latest alert concerning possible breaches in royal security. In September there was an embarrassing breach when an intruder was arrested after he had scaled a palace fence. An alleged accomplice was also arrested.
Just two days after those arrests police officers confronted the Duke of York in the palace gardens and demanded to know who he was.
The most serious incident was in 1982 when Michael Fagan managed to sneak into the Queen's bedroom.
The Associated Press contributed to this report