wedding dress

In the intervening time, duty may have lain more heavily on the future king's shoulders but the appetite for spontaneity remains.

Sleeping rough on the streets of London, in a woolly hat and hoodie, for a homelessness charity, or scrubbing lavatory floors during his gap year, the Prince has refused to be bound by protocol. It is a taste which has drawn constant comparisons with his mother, the late Diana, Princess of Wales, to whom he bears a striking resemblance.

Coming slightly less than a year after his parents' wedding, Prince William's birth on June 21, 1982, proved a global media sensation.

His father, the Prince of Wales, was almost lost for words, remarking that the baby looked "surprisingly appetising" with "sausage fingers just like me".

Joined by a brother, Prince Harry, two years later, his upbringing, though privileged, exposed him to normal life in a way unthinkable for past monarchs.

He was sent to Ludgrove prep school in Berkshire then Eton, and his parents strove to shield the young Prince from publicity.

Even now, as one of the most senior members of the Royal family, he regards the media with some suspicion, trusting a small circle of close friends and enjoying the fierce loyalty of his military comrades. It was while at Eton that William developed a reputation as a shy teenager, even as interest in his family's private life became more intense as his parents' marriage crumbled.

He was 15 when, in 1997, he was thrust back into the global spotlight in a way he could never have imagined, following his mother's death in a car crash in Paris.

The image of him towering over his 12-year-old brother as they followed her coffin remains one of the most memorable of the era. Although overt attention reduced after the tragedy, interest in the Princes never waned.

Aged 18 and with A-levels in geography, history of art and biology under his belt, Prince William embarked on a course similar to that of thousands of other middle-class young people, and took a gap year in Belize and Chile.

What glimpses the public had as he entered adult life – jungle training in Belize with the Welsh Guards or donning rubber gloves to clean floors – showed him far from the comforts of palace life.

At St Andrews University his quest for normality took him to a shared student flat where he relished doing his own shopping or cycling around town.

Initially feeling isolated, he toyed with leaving, but was talked out of it.

In a rare interview at the time, he laughed off his reputation as the world's most eligible bachelor, joking: "I've never been aware of anyone chasing me, but if there were, could they please leave their phone number?"

He explained his less than traditional approach to finding a future queen: "If I fancy a girl and I really like her and she fancies me back, which is rare, I ask her out. I don't have a steady girlfriend. Only the mad girls chase me, I think."

But his future bride was closer than even he might have imagined; Kate Middleton was one of his housemates.

Speculation about a romance began after the Prince was spotted kissing a girl with long dark hair at his water polo club's Christmas ball. Soon after, he was reported to have introduced a "Kate" as his girlfriend at a hunt meet.

Despite his reluctance to take the limelight, he was eager to make his sense of duty clear. He brushed off reports that he did not want to be king one day, remarking: "It's not a question of wanting to be, wanting is not the right word … It's a very important role, one that I don't take lightly."

While his brother's active social life drew negative comment on more than one occasion, William was careful to stay out of trouble.

In 2005, as his father was caught on microphone calling Nicholas Witchell, the BBC royal correspondent, an "awful man" during a photocall on the ski slopes, it was Prince William who diplomatically leant over and politely answered his question.

A few weeks later, as the Prince of Wales married the Duchess of Cornwall, William's prominent support – acting as a witness – did much to allay any potential controversy.

In recent years, he began to take on some royal duties. He made his first official overseas trip earlier this year, to Australia and New Zealand.

He is involved in a few carefully chosen charities, including the homelessness group Centrepoint.

For both Princes, a military career has offered the opportunity to serve in a normal profession while remaining out of the public gaze.

But while his brother served in Afghanistan, Prince William always knew that his potential value to an enemy made it unlikely he could follow suit. He left the Army for the RAF to work as a search and rescue pilot.

Prince Harry once wryly remarked that life on the front line was "about as normal as I'm going to get".

For his brother, the instinct is the same. On a recent visit to Africa he said he was drawn to remote parts of the bush because it offered him escape.

"The locals haven't got a clue who I am and I love that," he said.

As he prepares for a wedding likely to attract at least a billion viewers around the world, he might soon find that he is recognised even there.