As the US president arrives for a state visit under a massive security operation, Buckingham Palace's own arrangements have been called into question.
An undercover reporter revealed a flaw in Buckingham Palace security
For two months before President George W Bush arrived to stay inside the palace as part of his historic visit, an undercover reporter worked as a footman there.
Daily Mirror reporter Ryan Parry said he gained the job with a fake reference and had access to private suites, including the president's suite the night he arrived.
As part of the £5m security operation, all police leave has been cancelled, with thousands of extra officers on duty along with hundreds of armed US guards to ensure the safety of Mr Bush during his three-day visit.
Buckingham Palace security breaches
1982 - Michael Fagan enters
1989 - Mentally-ill Michael Crook walks past armed guards
1990 - Two separate break-ins
1991 - Man gets within yards of Queen's private apartments
1992 - Kevin McMahon arrested inside grounds twice in a week
1994 - Naked paraglider lands on palace roof
1995 - Student John Gillard rams gates with car
1997 - Absconded mental patient wanders grounds
2003 - Undercover reporter gains job as footman using fake reference
Following the revelation of the breach, Home Secretary David Blunkett announced a security review, focusing on the vetting of job applicants.
While the Home Office makes security and criminal checks, it is the responsibility of Buckingham Palace to carry out employment checks.
In the case of Mr Parry, the employment checks were "insufficient", Mr Blunkett told the House of Commons when announcing the review by the independent Security Commission.
John O'Connor, former commander at Scotland Yard told BBC News that security checks do not go far enough.
"It's difficult to point the finger at one officer or department, because the systems haven't been in place to conduct positive vetting.
"They need to make sure anyone employed by the royal household signs the official secrets act."
The security lapse comes after a breach at Windsor Castle during the 21st birthday party of Prince William, attended by the Queen and many senior Royals.
Aaron Barschak bypassed police, setting off six alarms and appeared on CCTV several times without sparking a response when he gatecrashed the party.
In a bizarre costume of peach-coloured dress and beard, police at the royal party assumed Mr Barschak was just another guest in fancy dress and let him in to the party.
The comedian was only arrested after he had interrupted a speech by Prince William, and kissed him.
Responsibility for the security of royal sites falls to the Metropolitan Police, who also provide the ever-present Royal Protection Squad, all experienced officers who are firearms and driving experts trained by the SAS.
Princess Anne was the target of a failed kidnap attempt in 1974 when a gunman forced her car to a halt.
Other royal security breaches
1992 - Intruder drinks whisky in St James's Palace
1994 - Break-in at St James's Palace;
2002 - Drunken intruder reportedly knocks on Princess Anne's door at St James's Palace
2003 - Man arrested in Windsor Castle grounds, man gatecrashes Prince William's birthday party in Windsor Castle
Both the Queen and Prince Charles have also had security scares involving firearms.
Blanks were fired at the Queen by a 17-year-old student during the Trooping the Colour ceremony in 1981.
And in 1994, a man firing a starting pistol rushed at the Prince of Wales during an open-air event in Sydney, Australia.
Perhaps the most famous security breach at Buckingham Palace was in 1982 when Michael Fagan broke into the Queen's bedroom.
The monarch woke to find Fagan, 30, sitting on her bed, and the pair reportedly chatted for half an hour before Fagan was apprehended.
In 1992 a helicopter carrying the Queen and Prince Philip was forced to divert as an intruder roamed the palace grounds.
Kevin McMahon, 25, was detained but undeterred, and broke into palace grounds again within the week.
In 1993, anti-nuclear protesters scaled palace walls and held a sit-down protest on the palace lawn.
The Queen woke to find Michael Fagan sitting on her bed
The following year saw perhaps the most bizarre intrusion, when a naked American paraglider landed on the palace roof.
In 1997 another security review was ordered after an absconded mental patient was found wandering the palace grounds.
Windsor Castle has also proved less than secure in recent years.
In 1994, a security review was launched after a ceremonial sword was stolen from the castle museum.
Days before, a pair of Eton schoolboys had scaled the castle walls and triggered alarms. Another man was arrested wandering in the grounds in April 2003.
Security at St James's Palace was described as "abysmal" in 1994, following a break-in at the Prince of Wales's apartment there.
Another inquiry was launched in December last year after an intruder broke in and allegedly knocked at Princess Anne's door, asking directions to Victoria Station.