Britain's Duke of Edinburgh will undergo an exploratory operation on his abdomen today.

A Buckingham Palace spokeswoman says it is a planned admission and the Duke is "in very good health." He turns 92 next week, and is set to remain at a Harley Street clinic for around two weeks.

Philip was driven to The London Clinic shortly after attending a garden party at Buckingham Palace.

The Duke missed an engagement at the palace on Monday night because he was feeling "under the weather" and had lost his voice, but officials said this was unrelated to his visit to hospital on Thursday.

The Prince was admitted to hospital twice last year because of a bladder infection that forced him to miss the last of the Queen's diamond jubilee celebrations.

He also suffered a blocked coronary artery the previous Christmas that required surgery.

On Thursday, ahead of the garden party, the Queen invested Prince Philip with New Zealand's highest honour, making him an additional member of the Order of New Zealand to mark the Diamond Jubilee.