The King’s most closely guarded possession is a pair of purple boxer shorts with little gold ducks on them, according to a former royal butler who spent 27 years in the household.

Mr Wilf Crump claims His Majesty wears them for every State Opening of Parliament. The tradition began when the King wore them to his first opening and got through the entire speech without losing his place.

“He’s credited the ducks ever since,” said Crump. “The speechwriter was furious.”

The morning the ducks went missing

Crump recalled one occasion when the shorts were still on the washing line twenty minutes before the royal carriage was due to leave.

“The King asked if we could delay Parliament. I said I could give them five minutes with a hairdryer.”

The carriage left on time. Crump said the King stood for the entire journey.

The Palace responds

Mrs Pritchard, head of the royal household, declined to discuss the King’s underwear. She did, however, dispute one detail of Crump’s account.

“They’re mallards,” she said.