David Belmar admitted trespassing and possession of a bladed article at Westminster Magistrates’ Court.
The 44-year-old from Haringey, north London, told police: “I wanted to see the Queen. I’m not happy about my benefits,” according to Edward Aydin, prosecuting.
He said Belmar, who has mental health issues for which he is taking medication, has a fixation with the Queen and received a caution in 1989 for lighting fireworks and throwing them into the grounds of Buckingham Palace.
The Queen was not in the building at the time of Monday’s incident, Buckingham Palace said.