The Elgin Marbles have survived an invasion by Turkish hordes and a bombardment by the Venetian Navy - but two rowdy schoolboys were too much for them, secret papers reveal.

The documents, released by the British Museum under the Freedom of Information Act, show that the 2,500-year-old antiquities have had to be repaired after a number of mishaps, acts of theft and vandalism by visitors.

The 2,500-year-old Elgin Marbles have had to be repaired

The papers, which were released at the behest of The Telegraph, also shed new light on the continuing battle for control of the antiquities, which were removed by the seventh Lord Elgin from the Parthenon between 1801 and 1804.

Some officials at the British Museum believe that their own institution is superior to the Parthenon and regard Lord Elgin as a hero who rescued the friezes from a Greek public unable to appreciate their worth.

In a letter to Tony Blair written in 2002, Sir John Boyd, the chairman of the museum's trustees, loftily dismissed the Parthenon as a "ruin that can never now be restored" - a comment likely to infuriate Greek public opinion.

Campaigners fighting for the restitution of the pieces will, however, seize on the disclosures about their damage to further their claims that the marbles would be better off in Greece.

They reacted with fury in 2002 when it was claimed that the chemicals used to clean the marbles in the 1930s had damaged them. The latest papers highlight nine instances of "minor damage" from the 1960s to the early 1990s.

In 1961 two schoolboys permanently damaged one of the 17 pediment figures in the museum's collection when they began fighting in the forecourt. One of the boys fell and knocked off part of a centaur's hind leg. The documents show that archivists were unable to replace "two small chips of marble" at the back of the leg.

Other pediment figures have also been damaged over the years. In June 1981, a workman from the Property Services Agency lost his balance and caused part of a glass skylight to fall on the west pediment figure. The accident caused "slight chips and scratches" to the top of the sculpture.

Damage to the antiquities are not down to accidents alone. In 1966 vandals scratched "four shallow lines" on the back of one of the figures, and in 1970 someone scratched letters on to the upper right thigh of another. Four years later, thieves damaged the dowel hole in a centaur's hoof trying to steal lead from it.

Despite such mishaps, both the Government and the museum insist that it is vital for the objects to remain in Britain.

In his letter to Mr Blair, sent in November 2002, Sir John wrote: "To remove any element of the collection - Egyptian, Mesopotamian, Greek, Roman, Indian, African, Mexican or Chinese - would be to dismember one of the very few places where the world can discover the world.

"This is a creative and living achievement of the Enlightenment. The Parthenon, on the other hand, is a ruin that can never now be restored."

In June 1997, Chris Smith, then culture secretary, told Dr Robert Anderson, then director of the museum: "Modern pollution on the Parthenon has caused tragic damage to those friezes which Lord Elgin did not remove... It is clear that the sculptures owned by the British Museum have benefited by being the property of the museum."

An internal museum briefing document states: "There is no evidence that the early 19th-century Greeks actually had any real sense of the archaeological or artistic importance of the sculptures."

Other papers reveal that in 2002 museum officials were worried that ministers might offer to loan the marbles to Athens in an attempt to gain support for their 2012 Olympic bid.

One unsigned internal memo from 2001 states: "Furthermore, there is little to be gained politically in securing a supportive vote for a United Kingdom Olympics in 2012 from the Greek delegation, since their vote alone would not secure the Games. This message needs to be get through to DCMS Ministers."

Museum officials appear to have fought a rearguard action to ensure that they and not the Government maintained control of the issue. They feared that any concessions by the Government would serve only to encourage other countries to seek restitution of their national treasures through diplomatic circles.

In an internal memo dated 2002, Dr Neil MacGregor, the British Museum's director, told a colleague: "I shall urge the Secretary of State to be extremely firm on the point that discussions be held only between museums. If once HM Government intervenes in a matter of this sort, the precedents for Egypt, Iraq, Nigeria etc become uncontrollable."

Dr MacGregor last night told The Telegraph: "When you put sculpture on public show you expose it to damage. Every museum in the world that has sculpture on public show has a record of regular damage.

"Graffiti, scratching, bumping whatever. You simply cannot put sculpture on show at a level where people can see it to study it without accepting the risk. It's the price you pay for making it available."

The British Museum said that it will make a number of documents available on its website - www.thebritishmuseum.ac.uk - later this week.