It was said to be made of soft white kid leather, given to him as a joke Christmas present by his younger sister, the Princess Royal.

But the Prince of Wales found his personal lavatory seat so comfortable that it was packed, at his insistence, every time he travelled abroad. Or so the rumour went.

Now, the heir to the throne has had his own say, apparently so frustrated by the absurdity of the claim that he could not help but swear.

"My own what?" he asked, incredulously, when asked about the allegation during a radio interview in Australia.

"Oh don't believe all that crap. The very idea."

The rumour was revived in a new biography, Rebel Prince: The Power, Passion And Defiance Of Prince Charles, by Tom Bower.