Two journalists who claim to have smuggled a fake bomb into Windsor Castle have put royal security back into the spotlight.
Armed patrols have not been enough to stop some intruders
The Sun reporters said they breezed past security just days before Prince Charles and Camilla Parker Bowles are due to have their wedding blessed in the castle.
The breach is the second in a week - last Sunday two tourists managed to gain access to private areas of the castle.
They are the latest in a long line of blunders at royal residences - some of which have seen intruders getting surprisingly close to Royal Family members.
Last September a Fathers 4 Justice campaigner dressed as Batman scaled a wall at Buckingham Palace and climbed on to a ledge as part of a protest over a court case.
Responsibility for the security of royal sites falls to the Metropolitan Police, who also provide the ever-present Royal Protection Squad - the Royal Family's bodyguards.
Met officers are tasked with securing the grounds and buildings within the perimeter, while the local force takes responsibility for policing beyond the gates.
Members of the Royal Protection Squad - all experienced officers who are firearms and driving experts trained by the SAS - are assigned to all key royals and never leave their side in public.
They have been called on to use their skills in the past.
Buckingham Palace security breaches
1982 - Michael Fagan enters
89 - mentally-ill Michael Crook walks past armed guards
90 - Two separate break-ins, one intruder claims Queen is his 'mum'
91 - Man gets within yards of Queen's private apartments
92 - Kevin McMahon arrested inside grounds twice in a week
94 - Naked paraglider lands on palace roof
95 - Student John Gillard rams gates with car
97 - Absconded mental patient wanders grounds
03 - Mirror writer Ryan Parry gets job as footman
Princess Anne was the target of a failed kidnap attempt in 1974 when a gunman forced her car to a halt.
One of her protection officers, who was shot and wounded during the incident, was decorated with the George Medal for bravery.
Both the Queen and Prince Charles have also had security scares apparently 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. The prince was unharmed.
But it is security at royal residences which has hit the headlines more recently.
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
Buckingham Palace, despite a strong security presence and armed patrols, has proved remarkably accessible to uninvited members of the public over the years.
Perhaps the most famous incident 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.
Many have followed in Fagan's footsteps, several suffering from mental disorders, despite the introduction of a sophisticated alarm system reportedly fitted in 1991 after another break-in.
Thought to include 24-hour monitoring and state-of-the-art sensors, this broadcasts "intruder in the grounds" at the first sign of a break-in.
The Queen woke to find Michael Fagan sitting on her bed
All windows are then closed, and security men rush to the scene of the breach.
But despite such measures, many others have succeeded in entering the palace.
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.
Some intruders have been politically motivated. In 1993, anti-nuclear protesters scaled palace walls and held a sit-down protest on the palace lawn.
The following year saw perhaps the most bizarre intrusion, when a naked American paraglider landed on the palace roof.
American James "Fanman" Miller was deported and fined £200 for the stunt.
In 1997 another security review was ordered after an absconded mental patient was found wandering the palace grounds.
In 2003, Mirror writer Ryan Parry got a job as a footman at Buckingham Palace using a false reference.
Mr Parry's identity was revealed by the paper the same day US President George Bush arrived in the UK for a state visit.
Mr Bush has been staying in Buckingham Palace, and the newspaper showed pictures of the bedroom used by Mr Bush and his wife.
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 the grounds in April 2004.
Throughout the 90s it was the subject of various security reviews including the introduction of laser beams and other sophisticated detection devices.
But in 2003 it had its most serious breach when Aaron Barschak gatecrashed Prince William's 21st birthday party dressed as Osama Bin Laden. He stood within feet of the Royal Family after scaling a wall.
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 after an intruder broke in and allegedly knocked at Princess Anne's door, asking directions to Victoria Station.