No rush to prepare William for crown

By Peter Hunt BBC royal correspondent

As Prince William's 21st birthday approaches, the BBC's royal correspondent looks at what the future holds for the young heir to the throne.

It's a brutal fact which Prince William probably rarely dwells on - for him to fulfil his destiny, his relatives have to die first.

William may wait many years to take the throne - longevity is in his family's genes

There's little prospect of the Queen abdicating - the last time her family went down that road in the 1930s, it was painful and potentially destabilising.

So, with his grandmother and father in robust health, the challenge is to find him a meaningful role.

All the indications, so far, are that his advisors aren't rushing to prepare the prince for the throne.

Their approach to his 21st birthday is very different to the one adopted when other royals celebrated such a significant milestone.

In 1947, the then Princess Elizabeth was on a state visit to South Africa. Her birthday, 21 April, was declared a public holiday and she attended a reception and a ball.

She also marked the occasion with a broadcast to the Empire in which she said: "I declare before you all that my whole life, whether it be long or short, shall be devoted to your service and the service of our great Imperial family to which we all belong."

The prince enjoys relative privacy while studying at St Andrew's

In the '60s, her son, Prince Charles, had delivered his first speech, in Welsh; been invested as Prince of Wales; and toured the country for a week before he turned 21.

Little wonder that he wrote in his diary afterwards that, "it now seems very odd not to have to wave to hundreds of people".

By contrast, William's 21st will be a low key affair. A visit to Wales; an interview; some photographs; and a private party. Plenty of fun, little talk - yet - of service.

It's clear Prince Charles feels he was burdened with the affairs of state from too early an age and he is determined to do things differently with his son and heir.

The student prince's short-term future is mapped out: He'll complete his degree; possibly spend a year in Africa; and maybe join the Army.

But how long before official portraits give way to paparazzi shots?

The attractions of the last option are obvious. Military barracks would give William the same protection from prying eyes he enjoyed at Eton and is now experiencing at St Andrew's University.

But at some stage in the not too distant future, Prince William will have to emerge from the shadows.

He'll be required to knuckle down and carry out royal engagements on his own. There will be pressure on him to deliver speeches. He will need to find a wife.

The "Firm" will want to exploit his glamour - he is a pin-up prince for the tabloids and he will have to establish a working relationship with the media.

Such a relationship will become more fractious, the more serious his girlfriends become.

Only once he's full-time royal, will we have any detailed sense of the real Prince William.

He may do more charity work in the developing world after graduation

For now, despite the acres of newsprint devoted to the subject, we know precious little about what really makes him tick.

He jealously guards his privacy: Friends who might be tempted to blab know that if they do, they'll be ejected from the inner circle.

There's talk of Prince William being a reluctant royal. It's easy as a young man to occasionally rail against your destiny. Much harder, in time, to reject what is on offer.

William Arthur Philip Louis Windsor, a future king, is in limbo. With longevity in his family's genes, he could be there for some time.