Camilla Parker Bowles has given an impromptu eight-minute interview to members of the British press covering the royal tour of India to mark her husband Prince Charles's 65th birthday.

It is by far the longest interview she has ever given, and she spoke in some detail about their lives together, describing him as an 'exhausting' workaholic who is impossible to buy presents for who never stops to 'chill out'.

"He never, ever stops working," Camilla said, "He’s exhausting. No matter what the day, he is always working.

“I am hopping up and down and saying, 'Darling do you think we could have a bit of, you know, peace and quiet, enjoy ourselves together’. But he always has to finish something.

“He is so in the zone. You are outside, but he is always there in the zone, working, working, working.”

The Telegraph reports that the 'impromptu' chat took place on an open first-floor balcony of the Aluva Palace hotel, and that the Duchess at times struggled to make herself heard because of the noise of a torrential downpour.

Speaking about his birthday today she said, “He’ll stick with his papers, I know he will, while I am trying to sing Happy Birthday. I might just even have to hold up a sign saying 'Happy Birthday, Darling’.”

Asked what the couple would be doing on their rest day, the Duchess said: “To be honest I think I am just going to chill out, completely, I don’t think I am going to do anything really.”

Would the Prince do the same?

“I shall do my best. If there’s a little hint of sun I might just persuade him to go for a walk or sit outside. He loves walking, so that might do it. We see the sun all the time but we never get the chance to just go and sit in it. So that would be bliss. So maybe I will persuade him. But no, my husband is not one for chilling.”