Fathers 4 Justice sparked an alert at Buckingham Palace in 2004
Buckingham Palace has suspended a chauffeur who allegedly gave undercover reporters access to sensitive areas of the building.
The incident appears to be the latest of a number of royal security breaches.
June 1981: Marcus Sarjeant, 17, fires six blank shots at the Queen as she rides along the Mall during the annual Trooping the Colour ceremony.
March 1982: Michael Fagan breaks into the Queen's bedroom at Buckingham Palace. She wakes to find him sitting on her bed.
1989: Mentally-ill Michael Crook walks past two armed guards at Buckingham Palace and tries to talk to the Queen near the stables.
1990: Stephen Goulding breaks into palace grounds. He claims he is Prince Andrew Windsor and says the Queen is his "mum".
July 1992: Kevin McMahon, 25, is arrested inside Buckingham Palace grounds twice in one week. His first foray forces the diversion of a helicopter carrying the Queen and the Duke of Edinburgh.
1992: An intruder walks into St James's Palace and drinks a whisky in Princess Alexandra's private apartment.
1993: Anti-nuclear protesters scale the walls of Buckingham Palace and hold a sit-down protest on the lawn.
1994: A naked paraglider lands on the roof of Buckingham Palace. American James "Fanman" Miller is fined £200 and deported.
1994: Security at St James's Palace is described as "abysmal", following a break-in at the Prince of Wales's apartment.
The Queen woke to find Michael Fagan sitting on her bed
1995: Student John Gillard rams the gates of Buckingham Palace in his car at 50mph.
1997: An absconded mental health patient wanders the grounds of Buckingham Palace.
December 2002: A drunken reveller enters St James' Palace late at night and reportedly knocks on Princess Anne's door, asking for directions to Victoria station. He is arrested before anyone can answer.
November 2003: Daily Mirror reporter, Ryan Parry, reveals details of life at Buckingham Palace after spending two months working undercover as a footman. He got the job using a false reference.
June 2003: "Comedy terrorist" Aaron Barschak gatecrashes Prince William's 21st birthday party at Windsor Castle. Wearing a dress, beard and sunglasses he gets up on stage and kisses the prince on both cheeks.
December 2003: A 27-year-old man is arrested in the grounds of Buckingham Palace after climbing a wall.
September 2004: Jason Hatch, a Fathers 4 Justice campaigner dressed as Batman, unfurls a banner on the balcony of Buckingham Palace.
May 2004: Michael Hammond cons his way into Windsor Castle by pretending to be a well-known senior police officer. He is jailed for four-and-a-half years.
April 2005: Journalists working for the Sun newspaper drive a van carrying a fake bomb into the grounds of Windsor Castle, days before the wedding of Prince Charles and Camilla Parker-Bowles.