Today's arrest at Buckingham Palace follows a number of security alerts - last month a suspected burglar managed to get into the building after scaling a fence.
He was found at around 10.30pm on 2nd September in a room that had been open to the public during the day.
A second man was arrested outside the Palace on suspicion of conspiracy to commit burglary.
Less than 48 hours later, amid heightened security, two police officers confronted the Duke of York in the Palace gardens demanding to know who he was.
Scotland Yard issued a public apology to the Duke, which he later accepted.
A man arrested trying to gain entry to Buckingham Palace was arrested at the North-Centre Gate which is used as the everyday entrance to the Palace.
Buckingham Palace said that the Queen was not in the building when the man tried to get in, but would make no further comment.
A man carrying a knife has been arrested trying to enter Buckingham Palace.
A 44-year-old man attempted to enter Buckingham Palace via the north centre gate but was immediately apprehended by police.
The man was searched and found to be in possession of a knife.
He was arrested on suspicion of trespassing on a protected site and possession of an offensive weapon.
Prince William kicked off the first football match at Buckingham Palace, joking that any players breaking windows would answer to the QueenRead the full story ›
Prince William took part in a training session at Buckingham Palace while the grounds hosted its first ever football match.
The Duke of Cambridge was put through his paces in some of the Queen's Household team's training exercises.
In the historic game, Polytechnic FC beat Civil Service FC by two goals to one.
The Civil Service team presented William with two tiny tops for his son, Prince George - one red and the other white, both with "HRH 1" on the back.
Prince William booted up to train on Palace grounds while England's two oldest amateur football clubs played a historic match.
The Duke of Cambridge trained with the Queen's Household team while the game was underway.
During the day the Duke of Cambridge, president of the Football Association, donned his boots - a present from England striker Wayne Rooney and embossed with WR10 - but not for the match, instead he joined the Queen's Household team for a training session.
England's two oldest amateur football clubs are busy warming up ahead of the first ever football match at Buckingham Palace.
Civil Service FC and Polytechnic FC, both based in Chiswick West London, are due to play a competitive Southern Amateur League fixture this afternoon.
Wembley groundsmen were tasked with preparing the lawn of the famous landmark for the occasion.