As Prince Philip marked his 90th birthday, the often-outspoken husband of Queen Elizabeth II said he's approaching his "sell-by date."

In a television interview broadcast to mark the celebration of his birth on June 10, 1921, Philip said he's finally ready to start slowing the pace of his public life.

"I reckon I've done my bit. I want to enjoy myself for a bit now. With less responsibility, less rushing about, less preparation, less trying to think of something to say," he told the BBC.

"On top of that your memory's going, I can't remember names. Yes, I'm just sort of winding down."

Philip, who is also known as the Duke of Edinburgh, married then-Princess Elizabeth in 1947.

According to royal watcher Richard Fitzsimmons, because Philip had no formal role under Britain's unwritten constitution, he has since had to carve out his own role in the royal family.

"He is an amazing public servant," Richard Fitzsimmons told CTV's Canada AM in an interview from London Friday morning.

"He has spent decades supporting the Queen, which he regards as his main function, and also the institution of monarchy."

To that end, Philip has acted as patron of approximately 800 charities and organizations. But now that he's slowing down, Philip has announced plans to remove himself from just 20 -- including the universities of Cambridge and Edinburgh where he is chancellor.

"But he will keep active. I mean, the man is a dynamo of energy," Fitzsimmons added, crediting the Duke of Edinburgh's upbringing for fostering his stamina today.

"His iron will dates back, I suspect, from a childhood which was extremely tough and over the years he's developed the most extraordinary resilience," he said.

Prince Andrew of Greece and Denmark and Princess Alice of Battenberg welcomed their fifth child and only son Philip into the world on the Greek island of Corfu.

But the Greek royal family was exiled when Philip was just 18 months. He went on to study in Britain and Germany before joining the Royal Navy College in 1939.

During that time, his maternal uncle Lord Louis Mountbatten first introduced the young prince to Princess Elizabeth. The two were actually distant cousins, as they both called Queen Victoria great-great grandmother.

After returning from distinguished service during the war, the two began courting. He subsequently renounced his prior royal titles, converted to Anglicanism and became a British citizen, opening the door to his marriage to Elizabeth in 1947.

In his ensuing record 59 years as consort, he has accompanied the Queen on all her Commonwealth tours and overseas state visits, and delivered an estimated 5,000 speeches along the way.

Yet it's some of his off-the-cuff remarks that have drawn the most attention.

Following a Royal Variety Performance in 1969, for example, Philip asked the singer Tom Jones if he gargled with pebbles.

"It is very difficult at all to see how it is possible to become immensely valuable by singing what I think are the most hideous songs," he said.

And he famously raised eyebrows in 1986, when he warned a British student in China he would get "slitty eyes" if he stayed much longer.

Then, during a 2002 trip to Australia, he asked a group of Aborigines, "Do you still throw spears at each other?"

Fitzsimmons acknowledges the notoriety of Philip's frequently politically incorrect comments, but laments them overshadowing his greater legacy.

"People tend to know him more than I necessarily feel they should for gaffes and quips," he told Canada AM, insisting his dedication to worthy causes merits more attention.

The Duke of Edinburgh award scheme, for example, has helped more than 6 million young people since its first incarnation in 1956.

In apparent recognition of the sacrifice he made to help the queen in her record 59-year reign, Philip will be bestowed with the title of Lord High Admiral of the Navy.

In another recent television interview marking his 90th year, Philip was asked to reflect on giving up his navy career when he married into the British monarchy.

"It was naturally disappointing," he said, recalling his resignation from navy life in 1951, the year before then-Princess Elizabeth acceded to the throne.

"I had just been promoted to commander and the fact was that the most interesting part of my naval career was just starting."

He maintained his connection with the Navy in the intervening years, taking up an appointment as Admiral of the Sea Cadet Corps in 1952, before a promotion to Admiral of the Fleet the following year.

And the position of Lord High Admiral is not the only new honorary title for the Duke of Edinburgh, after Prime Minister Stephen Harper announced his appointment as an Admiral in Maritime Command and a General in Land Forces Command and Air Command.

"His Royal Highness is currently Colonel-in-Chief of five Canadian regiments, and holds similar appointments with all three cadet organizations," Harper said in a statement announcing the appointment.

"He is truly an inspiration to us all and I know that all Canadians join me in extending congratulations to His Royal Highness on these appointments and best wishes for many more years of continued health and happiness."

Special activities marking Philip's birthday in Britain Friday included the Band of the Irish Guards regaling tourists gathered outside Buckingham Palace with a rendition of 'Happy Birthday.' There was also a 62-gun salute and the striking of a commemorative coin bearing Prince Philip's image on side and the queen's on the other.

Philip's royal duties continued, however, as he hosted an event for the Royal National Institute for Deaf People which is celebrating its own centenary.

At least he can look forward to a family fete over the weekend, with a reception planned for Windsor Castle on Sunday.

With files from The Associated Press