Britain's Duke of Kent, a cousin of Queen Elizabeth, is being treated in a London hospital after suffering a mild stroke, a royal spokeswoman said on Thursday.

The 77-year-old, who is cousin to the Queen through his maternal grandfather, Prince Nicholas of Greece, is recovering well after he fell ill early on Monday (local time).

"He hopes to be out of hospital in the next few days," a Buckingham Palace spokeswoman said. "His programme has been either postponed or cancelled for the next three weeks."

The Duke of Kent, who inherited his title at the age of six when his father died in a plane crash during World War Two, has been president of the Stroke Association for more than 20 years.

"Our thoughts are with him and his family and we wish him a very speedy recovery," the charity's chief executive Jon Barrick said in a statement.

Buckingham Palace gave no more details about the royal's stroke. Queen Elizabeth spent time in hospital earlier this month with a stomach bug.

Born in London in 1935, the Duke of Kent was educated at Eton College, the prestigious school west of London attended by Princes William and Harry and Prime Minister David Cameron.

After serving in the military for 21 years, he took on a role promoting British trade as well as representing the Queen at official events.

As president of the All England Lawn Tennis and Croquet Club, the father of three is a regular at the Wimbledon tennis championships each summer. He is also president of the Royal National Lifeboat Institution.

The duke has been a senior freemason for decades, holding the position of Grand Master of the United Grand Lodge of England since 1967.

- Reuters