United Kingdom - A suspected burglar has been arrested after being discovered in a royal state room at Buckingham Palace.
Police said the man was found 'in an area currently open to the public during the day' after scaling a 12ft fence to get into the palace.
A security review has now been launched following the break-in.
No members of the royal family were present at the palace at the time of the incident.
The man has been arrested for burglary, trespass and criminal damage.
A second man was arrested outside the palace for conspiracy to commit burglary following the incident shortly before 10.30pm on Monday.
According to reports, police and security rushed to the palace after motion sensors were set off.
A spokesman for the Metropolitan Police said: 'Both men have been bailed to return to a central London police station and enquiries continue.
'A review of the specific circumstances of this incident is being carried out.
No members of the Royal Family were at Buckingham Palace at the time of the incident.'
A spokesman added that security would form part of the review.
According to The Sun, a source close to the investigation said: 'This breach of security is being treated with the utmost seriousness.'
Buckingham Palace have not commented on the incident.
The Queen has been spending her summer break at Balmoral Castle since the beginning of August and is not expected to return to the palace until October.
She is expected to make her traditional appearance at a Highland Games today.
The Braemar Gathering is held each year just a short distance from the Balmoral estate in Aberdeenshire.
The break-in is one of the most serious security breaches at the palace since 1982, when Michael Fagan evaded guards to get inside the Queen's private chambers while she was still in bed.
The unemployed father of four, 31, spent around 10 minutes talking to the Queen after he climbed over the palace walls and up a drainpipe.
The Queen managed to raise the alarm when Fagan asked for a cigarette, allowing her to call for a footman who held him until police arrived.
The break-in at Buckingham Palace is the latest in a series of security scares involving the Royal Family.
In March 2011 a car carrying the Prince of Wales and the Duchess of Cornwall (below) was mobbed by demonstrators who had split from a protest against higher university tuition fees.
Camilla was visibly distressed after being poked in the ribs with a stick through an open window in the distinctive Rolls-Royce Phantom VI as she and Charles travelled to the Royal Variety Performance at the London Palladium.
In 2003, comedian Aaron Barschak managed to get into Prince William's 21st birthday party at Windsor Castle.
The self-styled 'comedy-terrorist' set off a series of alarms and was caught on CCTV before he joined 300 guests at the bash and was removed.
In 1994, student David Kang charged at Charles while firing a starting pistol during a ceremony in Sydney, Australia.
Kang was wrestled to the ground by New South Wales premier John Fahey and another man, while Charles was praised for his calm reaction.
In 1981, six blank shots were fired from the crowd while the Queen rode during the Trooping the Colour ceremony.
The Queen's horse was startled but she managed to bring it back under control while police rushed to grab the shooter.
In 1974, Princess Anne was the target of an apparent kidnap attempt in The Mall near Buckingham Palace.
Four people, including her bodyguard, Jim Beaton, were injured after shots were fired when their car was forced to halt by another vehicle which blocked their route.
A police officer chased the driver, Ian Ball, and brought him to the ground before arresting him.
Buckingham Palace is the official London residence and principal workplace of the British monarch.
Located in the City of Westminster, the palace is a setting for state occasions and royal hospitality.
It has been a focus for the British people at times of national rejoicing and crisis.
Originally known as Buckingham House, the building which forms the core of today's palace was a large townhouse built for the Duke of Buckingham in 1705 on a site which had been in private ownership for at least 150 years.
It was subsequently acquired by George III in 1761 as a private residence for Queen Charlotte, and known as "The Queen's House".
During the 19th century it was enlarged, principally by architects John Nash and Edward Blore, forming three wings around a central courtyard.
Buckingham Palace finally became the official royal palace of the British monarch on the accession of Queen Victoria in 1837.
The last major structural additions were made in the late 19th and early 20th centuries, including the East front, which contains the well-known balcony on which the royal family traditionally congregates to greet crowds outside.
However, the palace chapel was destroyed by a German bomb in World War II; the Queen's Gallery was built on the site and opened to the public in 1962 to exhibit works of art from the Royal Collection.
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