In one of the more comical incidents, at the National Portrait Gallery, the ornament on a frame around a painting of John Dryden, the 17th century poet, by James Francis Mauber valued at £25,000 was detached after a visitor who was part of a large tour group was accidentally knocked off balance by a security officer and fell onto it.

At the British Museum, a 17th century Edward East night clock was broken when a visitor lost their footing and knocked it over, while a valuable Japanese clock was damaged after a cleaner accidentally stumbled into it during a power failure.

But Tate Modern is also a repeat offender.

Roy Lichtenstein’s painting Whaam!, one of the earliest works of pop art which depicts an exploding plane, was defaced when one visitor decided to dispose of what was thought to be chewing gum on the picture itself rather than in a nearby bin.