Prince William's future has always been mapped out but as fatherhood nears, the 31-year-old shows little sign of giving up the semblance of a normal life he has carved out for himself under the media spotlight.

The eldest son of Prince Charles and Diana, William knew from an early age the duties that await him as second-in-line to the British throne, even if he did not expect to inherit the crown for decades.

Yet despite the weight of expectation and the trauma of losing his mother in 1997, the Duke of Cambridge has balanced royal ribbon-cutting, a military career and a personal life of his own choosing.

William is a Royal Air Force (RAF) search-and-rescue helicopter pilot in Wales, a job that also gives him the privacy to live with his wife, the former Kate Middleton, away from the world's media.

Their marriage in April 2011 was a global event, but William delayed tying the knot for almost a decade to ensure the match was right, just as the couple then waited for two years before starting a family.

Aides say he has always fought to do things his way. "You have to be slightly stubborn because everybody wants you for one reason or another," William once said.

The prince was born on June 21, 1982 into a life of wealth and privilege, although Diana ensured he and his younger brother Harry did not suffer the rather cold upbringing endured by their father.

She showered the boys with affection and, although they were brought up in a palace by nannies, took them on official trips and to charity events to see how ordinary people lived.

William has Diana's gift for engaging with people and is also an assured and often amusing public speaker.

To the outside world, he appears remarkably well-adjusted, a small miracle given his parents' acrimonious and highly public divorce and Diana's sudden death in a car crash in Paris when he was only 15.

William was drawn into the couple's power games and was his mother's confidante, pushing tissues under the bathroom door as she sat sobbing inside.

But he emerged with a warm memory of Diana and a good relationship with Charles, but also with what one aide said was an "innate sense of self-protection".

William's early hatred of the media which he believed harassed his mother has given way to grudging acceptance, but he tries not to give them too much to write about.

He was widely criticised in 2007 when he borrowed an RAF helicopter to fly to a stag weekend, while a few stories have emerged of his student drinking and "roving eye".

Pictures of him dancing with a mystery blonde in a nightclub contributed to a brief split from Kate, whom he had met at university several years previously.

But broadly William has kept his image and his interests clean, from sport -- he is a fan of Aston Villa football club and has played everything from rugby to polo -- to indulging his passion for motorbikes.

Although he has always been in the public eye, he has had long spells of time away from the cameras.

He spent much of his childhood at boarding school, including the elite Eton College, before taking a year off in Belize, Chile and Kenya.

William returned home to study at the University of St Andrews in Scotland, where a deal with the media to leave him alone resulted in four years of unparallelled freedom.

William graduated with a degree in geography and joined the army, a well-trodden career for a prince who will one day be commander-in-chief.

He wanted to serve with British troops in Afghanistan, like Prince Harry, but it was considered far too dangerous for a future king.

William instead spent time in all three branches of the armed forces before settling on the RAF search and rescue service, perhaps the most challenging military job away from the front line.

But William remains a prince, and must decide this summer what to do after his RAF job comes to an end. It remains to be seen how long he can balance his two lives.