Diana, Princess of Wales and her younger sibling Charles, had their heads bashed together and banged against a wall if they misbehaved, the book claims.

Written by the now Earl Spencer, the memoir has already ignited a war of words with the Royal Family over claims King Charles III said Diana would "soon be forgotten" after her death in a car crash in Paris at the age of 36 in August, 1997.

But away from the storm which has seen Buckingham Palace drawn into an incendiary row over is contents, the book Swan Song: Diana, My Sister, makes fresh claims about the siblings' childhood at Park House on the Sandringham Estate, near King's Lynn.

Life in the sprawling property close to the Royal Family's retreat was sometimes less than idyllic, with some of the young Spencers' succession of nannies inflicting physical punishments behind the backs of their parents.

One would bang the children's head against a wall if she deemed them naughty, the earl alleges.

"If we were both to be punished, this nanny would stand us next to one another, grab us both by the hair and bang out heads together with surprising strength," Earl Spencer writes.

A cricket game in progress at Sandringham, with Park House in the background (Image: Chris Bishop)

"The shock of these strikes was enormous and would leave us both in tears. But we were never broken by the cruelty."

Another "hatchet-faced harridan" would wield a wooden spoon with great force.

The book says while Diana and Charles's mother Frances lived at Park House, before she left their father John Spencer and moved out in 1967, a closer eye was kept on the couple's four children.

"One of our sisters' nannies had been sacked on the spot after mother became mystified by how frequently her two eldest children, Sarah and Jane, suffered from stomach........

© Eastern Daily Press