In rare public comments about his grandparents, Harry highlighted the role of Prince Philip in supporting the queen on her many duties, including occasional visits abroad and hosting foreign dignitaries. He also paid tribute to the monarch's hard work ethic despite her age.

"These are the things that, at her age, she shouldn't be doing, yet she's carrying on and doing them," he said in an interview with The Radio Times published Tuesday.

"Regardless of whether my grandfather seems to be doing his own thing ... The fact that he's there — personally, I don't think that she could do it without him, especially when they're both at this age," Harry added.

At 85, Elizabeth is Britain's second longest-serving monarch after Queen Victoria. Her 60th year on the throne — called the Diamond Jubilee — will be celebrated this year in major events both in Britain and in Commonwealth nations around the world.

The monarch has been supported in most of her duties and overseas trips by Philip, who turned 90 last June. Although he had expressed a desire to scale down his royal engagements, last year the pair still made a historic trip to Ireland, hosted a state visit by U.S. President Barack Obama and visited Australia on a 10-day tour.

Philip, who is known to be active and robust, suffered a health scare before Christmas when he went to the hospital complaining of chest pains. He recovered after undergoing a successful coronary stent procedure.

The royal has resumed his official duties and in the next few months, he will accompany the queen on travels throughout Britain, while their children and grandchildren plan to travel around Commonwealth countries to mark the Jubilee.

Harry's comments were part of a series of interviews conducted for an article on the queen published in the Radio Times. The report also quoted Prince William, Prime Minister David Cameron and his predecessor Tony Blair on their impressions of the monarch.