Back in the 1980s it was a popular pastime to collect desk rubbers - from the smelly ones to the unusually shaped. But it was rare to spend more than about Pounds 2 on building a hoard.

So it was an unusual development last week when a large desk rubber bearing the words “For Big Mistakes” sold at auction for Pounds 540.

But the eraser did not belong to any pupil - in fact, it was Princess Diana’s when she was a nine-year-old pupil at Riddlesworth Hall, a boarding school in Norfolk.

The auctioneers said Diana had scrawled all over the rubber “D Spencer” ... “Diana” and “Beware Bomb, Help!” It was among other royal memorabilia being auctioned by Reeman Dansie in Colchester, Essex.