By Natasha Grüneberg
BBC News Profiles Unit
In the year the Queen has celebrated her 80th birthday with fanfare and celebrations, her husband, Prince Philip, Duke of Edinburgh, is turning 85 in a much quieter fashion.
The Duke of Edinburgh: Still going strong at 85
At his wife's side throughout her reign spanning more than half a century, Prince Philip has carved out a role for himself while supporting her.
He was born on the Greek island of Corfu on 10 June 1921, a member of the royal family of Greece, despite having no Greek blood. His family tree includes members of the royal families of Denmark, Germany, Russia and Britain.
He went to Gordonstoun school in Scotland, where he later sent his sons. On leaving, he became a naval cadet at Dartmouth because, as he put it, "the war was coming up and you might as well get started right".
During World War II, Prince Philip saw action as a Midshipman on the battleship HMS Valiant. When the Italian fleet was trapped off the southern tip of Greece in 1941, Philip manned a searchlight to illuminate the enemy ships and was mentioned in despatches.
Prince Philip's naval career continued after he married Princess Elizabeth in 1947, but the poor health of the King, George VI, meant that the young couple had to take on more public duties.
Prince Philip had a distinguished career as a Royal Navy officer
In later life, Prince Philip said he was sorry that he had been unable to continue his career in the navy.
The Duke of Edinburgh was someone who might have reached the highest levels in the Royal Navy, and contemporaries have said that he could, on his own merit, have risen to be First Sea Lord. But he had to abandon his own ambitions to support the Queen.
In his own right, though, Philip has pursued his own interests in three main fields: science and industry, the welfare of young people and the environment.
To many people, especially readers of the tabloid press, the first thing that springs to mind about Prince Philip is a caricature of a gaffe-prone prince.
He has been taken to task by the press for comments but they have rarely caused genuine offence and over more than half a century of public service, that could be seen as remarkable in itself.
PRINCE PHILIP'S WIT & WISDOM
"Where did you get that hat?" (1953) To the Queen, after her Coronation
"French cooking's all very well, but they can't do a decent English breakfast." (2002)
"If you see a man opening a car door for a woman, it means one of two things: it's either a new woman or a new car!" (attrib)
The prince has spoken his mind on many occasions, which has sometimes got him into trouble, but often he has merely been articulating what many people have been thinking.
In 1961, he was blunt about British industry, telling industrialists "Gentlemen, it's time we pulled our fingers out."
In an interview in November 2004, Prince Philip's grandson, Prince William, said he had a close relationship with the Duke, and he admired his occasional bluntness. "He will tell me something I don't want to hear and doesn't care if I get upset about it. He knows it's the right thing to say."
One of Prince Philip's most popular legacies is the Duke of Edinburgh Award Scheme, which he launched in 1956 to encourage a spirit of initiative, adventure and self-discipline among young people.
The Prince presents a Duke of Edinburgh Gold Award in Jamaica in 1998
Since then, more than three million youngsters in the UK have taken up the challenge, and the scheme has become one of the most successful youth programmes in the world.
He was closely involved in developing the scheme to include skills, hobbies, physical recreation and service to the community. All the things which he believed the average well-adjusted adult must have in their armoury to face life.
Prince Philip has also lent his support to the World Wide Fund for Nature (WWF), following his own fascination with the natural world. He is particularly interested in the preservation of species and brought drive and determination to his role as the charity's president.
He wrote his own speeches, not even wanting the charity to draft them for him.
Sporty royal: Philip is passionate about carriage driving
From his earliest years, the Duke of Edinburgh has been a keen and talented sportsman. He excelled at cricket, sailing, polo and carriage-driving. He took up carriage driving, as a "geriatric sport", after retiring from polo in 1971.
He says he thought it would be "a nice weekend activity, rather like a golfing weekend. Which it was, until some idiot asked me to be a member of the British team."
Arthritis prevented him from carriage driving for a while, but now he is back behind the horses and still competing.
Although Prince Philip has spent his public life two paces behind his wife, the Queen defers to him in private. A member of his private staff who has worked with him for more than a decade says "The Queen wears the crown but he wears the trousers."
Throughout the travails of the royal family he has remained a steadfast support to the Queen while remaining very much his own man.