By Paula Dear and Martha Buckley BBC News

Prince Harry passed rigorous tests to win a place at Sandhurst

Prince Harry has already enrolled at Sandhurst and Prince William has indicated he might want to follow him into the Army.

If he did join up, the second-in-line to the throne says he would not want to be shielded from danger because of his position.

But can the princes ever be treated the same as ordinary soldiers?

While they may not expect special treatment, it is possible the princes might be viewed as a liability if sent to fight in Afghanistan or Iraq.

Apart from the risk of them being killed or injured, there is the possibility their presence might put others in danger, by provoking attacks.

The risk of them being kidnapped must also play heavily on the minds of army commanders who consider deploying them in risky parts of the world.

Hugo Vickers, royal correspondent and author, said: "With William, I believe he is totally sincere in wishing to go to the front line and of course the Army would want him to serve. But if I was in command, I would think twice about exposing him to unnecessary risk.

A clever commanding officer would probably keep them [the princes] busy and let them feel that what they were doing was important enough Hugo Vickers What's in store for Harry at Sandhurst?

"Things going on behind his back would mean it would probably never happen."

However, in general training away from actual conflicts, the princes would be treated like everyone else, he added.

Mr Vickers said: "If they did get special favours we'd probably hear about it, because in every walk of life there are disenchanted people who would talk. I believe this is one area where they don't get special favours.

"A clever commanding officer would probably keep them [the princes] busy and let them feel that what they were doing was important enough."

Major Charles Heyman, senior defence analyst for Jane's Consultancy Group disagrees, saying the princes should have to do "all the normal things".

He said: "Otherwise there would be a public outcry. People would say 'Why should our sons be put at risk when theirs are not?'

"If you were commanding the heir to the throne, obviously you're going to see him slightly differently but you'd have to make even more of an effort to treat them the same, or that would be your crime.

Prince Andrew saw active service in the Falklands

"It is a tremendously egalitarian society now, not like in the days of the Duke of Windsor, when he was kept back from the front line."

If one of the princes was treated differently, he said it would lead to "rock bottom" morale among their fellow officers and the rest of the unit.

And his respect as a leader would "go out the window". He added: "People think officers tell soldiers where to go and what to do but leadership is really about 'follow me'. No one will do anything unless you get up and say 'Follow me.'"

If he was the princes' commanding officer, Major Heyman says he would worry neither more or less about what happened to them than about any of his other troops.

He said: "At the end of the day, it's a career and it's not a crime for one of your soldiers to be injured or killed.

"Whether it's the heir to the throne or an infantryman from down the road, it would hurt the same.

"If I was the commanding officer, I would be only too pleased to give them the job they wanted to do."

Whether they get to see front line action or not, Mr Vickers thinks military training will stand the princes in good stead.

He said: "It will teach them how to think in a certain way - the way the military mind works. It may sound trivial but it's things like the mere rules of punctuality, the attention to detail, the ability to think and plan ahead.

It is a tremendously egalitarian society now, not like in the days of the Duke of Windsor, when he was kept back from the front line Charles Heyman

"These things will work well outside the military, Prince Philip has that kind of logical mind which he has applied to all sorts of things, like the Duke of Edinburgh Awards Scheme."

Though he may not be allowed to see much active service, serving in the Army would least give Prince William a sense that he has earned the right to wear military uniform, which has often been given to royals who have not served their time.

Mr Vickers said: "It's awful when they have not earned their uniforms in any way."

Being in the Army may also give the princes an extension of the sort of freedom from media intrusion they have enjoyed during their studies, as the press and public are less likely to know where they are.

"They are much more likely to get confidentiality there than in civilian life. They are dealing with secrets, " Mr Vickers added.

There was a time when kings and princes routinely went into battle, with some of them killed or injured in the process.

The Duke of Windsor had to 'escape' to see the trenches

King Harold famously died during the Battle of Hastings in 1066, Richard Lionheart fought in the crusades in the twelfth century and Richard III was killed at the Battle of Bosworth Field in 1485.

The last British monarch to actually lead troops on the battlefield was George II against the French at Dettingen in 1743.

In modern times, military participation by senior figures has been carefully managed, rarely allowing them near the forefront of the action.

Edward, Duke of Windsor, served as a staff officer in World War One while he was heir to the throne but was not allowed to fight on the front line.

Lord Kitchener famously remarked that even if he was convinced the duke would be killed, he would not necessarily stop him going but that he was worried about him being kidnapped and used as a pawn.

Mr Vickers said: "It was a source of great frustration for him but inevitably, if you are his commanding officer, it is more trouble than it's worth having someone like him getting into difficulties."

According to Mr Vickers, the Duke often suffered for being a royal prince in the Army, having his hair dyed red and various pranks played upon him.

But he did go some way to fulfilling his ambitions by "escaping" several times to see the trenches.

The duke's younger brother, Albert, who later became George VI, saw some action in World War I when he served as a junior officer on board HMS Collingwood in the Battle of Jutland.

Another brother, the Duke of Kent, was killed in a plane crash in Scotland while serving in World War II.

A more recent precedent has been set by William and Harry's uncle, Prince Andrew, who had a 20-year career in the Navy after joining in 1979.

During this time he served on board HMS Invincible during the Falklands war, where he did get a taste of real action, flying on missions and helping evacuate casualties.