How to live like a prince: the shabby style, Sloaney slang and social rules of William and Harry's inner circle

To make a Treasure Chest, you tip half a litre of vodka into a wooden box full of juice, ice cubes, and chopped fruit. Then you pour in an entire bottle of champagne. At a Mayfair night-club called Mahiki, punters drink the resulting mixture through long communal straws before trying not to fall over on the dance-floor.

Right now, the Treasure Chest is Britain's most notorious cocktail, and not just because of its £100 price tag. It has achieved fame as the favourite tipple of Prince William and Prince Harry, who in turn are London's most famous party animals. Mahiki, a Polynesian-themed boite near Berkeley Square is Wills and Harry's favourite night-club and therefore a prime stomping ground for the modern Sloane ranger.

If a social anthropologist were to descend the staircase there one Thursday, which the club's owner Piers Adam describes as "our biggest Sloane night", he would find it packed to the rafters with square-jawed young versions of the heirs to our throne. They wear jeans, shirts and jumpers from Ralph Lauren, or Jack Wills, or Abercrombie and Fitch. They speak public school, with a smattering of estuary. They work hard, play hard, and party even harder.

Related articles

• James Colthurst: The real lessons of my friend Diana's death
• Interviews: Harry speaks candidly about Diana's death
• Search the news archive for more stories

As, it seems, do the two princes. Take, for instance, the antics of William, on the night his split from girlfriend Kate Middleton became public. Having strode across Mahiki's dancefloor shortly after midnight, he declared "I'm free!" before sitting a group of friends down at one of the rattan tables with the immortal words: "C'mon chaps, let's drink the menu!"

The incident was all over the next day's papers, which in turn sparked a minor trend in twentysomething toffs attempting to work their way through the dozen or so cocktails on the night-club's menu (it costs of roughly £350 a head, but luckily most drinkers boast small trust funds in addition to their graduate incomes). It also saw whole tribes of willowy girls descend on the venue hoping to snare the newly single future monarch. Such is the pulling power of a young royal.

Little wonder, then, that Prince William and Prince Harry suffer from an image problem. If you believe what you read in the papers, they are little more than cocktail-swigging hellraisers, who have devoted their early twenties to staggering up red carpets and past velvet ropes outside exotic venues in west London with names like Boujis, or Mamalanji.

Every time their nocturnal antics are photographed, a minor brouhaha ensues. Last Sunday, photos of Harry canoodling with fake-breasted barmaids from a nightspot in Calgary, where he is away (supposedly) on Army training, were on the front page of the News of the World. His reported question to one blonde - "are you wearing any underwear?" - sat uneasily next to news that the 150th British serviceman had just been killed in Iraq.

Yet a forensic examination of their lifestyles paints a less straightforward picture. At 24 and 22, William and Harry are in fact only occasional partygoers. However much they might enjoy night-clubs, William has actually been photographed visiting them just nine times this year; for Harry, the figure is a more modest eight.

This month, we are to be bombarded with further evidence for the princes' defence. They have given two TV interviews to publicise the concert being held on 1 July at Wembley Stadium to mark the tenth anniversary of Diana's death. One is with NBC's veteran news anchor, Matt Lauer, the other with the BBC's Fearne Cotton. Both were stage managed by their private secretary, Jamie Lowther-Pinkerton, and press secretary, Paddy Harverson. NBC trailed highlights of the on-the-record interview on their internet site on Friday; the full effort will be screened tomorrow.

"You will see two grown-up men talking for the first time about their childhood and their mother, and the real experiences of their young adult life," I'm told. "If you (omega) watch it all the way through, you'll realise that it's the first time they've properly opened up. People will be surprised by how much they've grown up, and also by the strength of brotherhood between them."

The aftermath of the Wembley concert will also see the stepping-up of their military career. William will complete his troop-leader training, and return to his regiment, the Blues and Royals, which is part of the Household Cavalry. Harry, who is a coronet, or second lieutenant in the same regiment, could be off to war.

Both will then be eased into minor royal duties, which will be arranged to compliment the official interests detailed on Clarence House's internet site. William likes football and swimming, and supports homeless and conservation charities; Harry's passions are rugby, polo, music and off-road motorbiking.

The princes' lives are therefore heavily compartmentalised. On-the-record they are reflective and dutiful. Off-the-record they are still young and occasionally prone to excess. In reality, for all their fame and fortune they remain enigmas: aloof, unknown, and more or less unknowable.

"The princes have a friends bit of their lives, and a duty bit of their lives, and they keep the two completely separate," says the Tatler editor Geordie Greig. "When they are in Palace mode, they are advised and looked after by a bunch of quite clever middle-aged men, who are thinking about big issues of monarchy, and the future of the state."

"They are also the most media-savvy generation of royals we've ever had. "They are very aware that what's said and shown can have a huge resonance." Perhaps, then, the only way inside the princess' real lives is to peep behind the floppy fringes of their heavily guarded social world.

The problem with trying to understand what makes William and Harry tick is that we already know too much. Like doting grand-parents, we were shown photos of their first days at school, or trips down log flumes at Thorpe Park during half term. We watched their parents' marriage steadily disintegrate, and wept when their childhood ended forever on 31 August 1997, with the death of Diana, their mother, in a Paris underpass. Their youth has been a sort of soap-opera; such is the nature of royalty.

Received wisdom has it that William is quieter and more guarded than his younger brother, who grew up unburdened by the pressure of having to one day assume high office. William is also more academic, having gained a 2:1 in history of art from St Andrews University. Harry, who was in bottom sets at Eton, left with a "B" and a "D" at A-Level.

"People have often remarked on the difference between them," says a senior Clarence House aide. "It is fair to say that, as with a lot of brothers, the elder is studious and thoughtful, and the younger is looser and more outward-going. There is an element of that, though Harry has matured considerably since joining the Army."

A contemporary of both princes at Sandhurst adds: "Although everyone thinks of it as a finishing school for posh boys, Sandhurst is actually a melting pot. Only about 15 per cent of its intake come from public school, and they did themselves no harm by mixing with the other 85 per cent, and showing they could be perfectly good soldiers."

Harry treats the Army as a career, and intends to spend as much as a decade in the Blues and Royals, a light cavalry regiment that specialises in reconnaissance in Scimitar tanks. Though disappointed at having been prevented from serving in Basra, for security reasons, he recently flew to Calgary for training, and is now expected to join a tour of Afghanistan.

William, who is currently training at Bovington in Dorset, has by contrast been told (and happily accepts) that he will never serve on the front line. Like his brother, and in a break from royal tradition, he draws an Army salary of around £30,000. "William is a future king, and therefore head of the armed forces," says a royal aide. "After the initial training, he will do a stint with the Navy and RAF. After that, he'll take up more royal duties. If we're being really honest, he isn't as enamoured with Army life as his brother anyway."

Away from the workplace, William is also in a period of flux, having separated from his girlfriend of four years, Kate Middleton, earlier this year. Acquaintances say he has recently cut a strangely uncomfortable figure.

"Say what you like about Harry, he's pretty straightforward," says one. "The funny thing about William is he's actually rather boorish. I've sat on tables at weddings with him, and he'll tell slightly sexist jokes, and then look embarrassed. He can be pretty awkward. Not as awkward as his dad, but he's inherited quite a lot of that."

Other acquaintances have suggested that splitting from Middleton marked a sort of early midlife crisis. "William is not as self-confident as you'd think," says one. "Here is a guy who basically reached his physical peak at 16. Everyone fancied him, and it's been downhill all the way since then." Harry, by contrast, has matured well. He boasts a bombshell girlfriend in the shape of Chelsy Davy, whose only fault is her father Charles's links to Robert Mugabe's regime.

Though they will now divide free time between the Blues and Royals HQs in Windsor and Knightsbridge, William and Harry never really relax under the bright lights of London. Home for them is actually around their father's country seat, Highgrove in Gloucestershire. The local social circuit revolves around pubs and restaurants like the the Vine Tree at Norton, and Cat and Custard at Shipton Moyne. It's very public school, and a lot of their teenage girlfriends came from (omega) Westonbirt, which is just across the road from Highgrove.

William drives a motorbike when in the country (he enjoys the anonymnity of being under a helmet) and both Princes are fastidious about paying their way in local hostelries.

"There's a polo set, and a hunting set, and they all intermingle in Gloucestershire," says one local. "William and Harry also turn up at a lot of house parties, and although there will be a bodyguard, they can behave in a normal fashion. It's something they can't really do anywhere in town."

The princes have spent much time at the Beaufort polo club, run by the former cavalry officer Simon Tomlinson and his wife, Clare. Their two sons, Luke and Mark, are close chums, as are the four sons of Norfolk landowner Hugh Van Cutsem, together with a smattering of headline-prone Londoners such as Richard Branson's children, Holly and Sam.

"I bumped into William in a pub once, and had a drink with him," says the royal writer Penny Junor, author of The Firm, who lives near to Highgrove. "He struck me as nice thoughtful person, and very good fun. But obviously, he was very wary."

Both princes expect absolute loyalty from even minor acquaintances, and as a result tend to draw friends from families, schools and backgrounds that they can rely upon. Having often been betrayed in the press, they are said to rate people not according to whether they like them, but to whether they can trust them.

"Friends will simply not talk about them, not even to say nice things," adds Junor. "I'm not sure how this has happened, and it's certainly not co-ordinated. I think their friends just don't want to be seen kissing and telling."

As a result, she says, they were both able to sow wild oats during their teenage years, doing normal adolescent things like drinking, smoking and sex. "Harry, in particular, had girls literally queueing up at hunt balls and took full advantage. It's been quite indiscriminate, but because of who the girls are and what they have to lose, nothing ever gets out."

In this respect, they are no different from royals of previous generations, though their indiscretions have been more public. "The Queen had house parties and they had a hell of a time, but they were just more discreet," says Robert Jobson, the Evening Standard's influential royal correspondent.

"William and Harry are two single guys who are entitled to do what they like, and most people accept that. They enjoy it, and the one thing they have from Diana's legacy is that it has given them a lot more freedom than other generations, and they've taken full advantage of it. Good luck to them."

Back in London, it's difficult to exaggerate the extent to which William and Harry's tastes influence the town's posh nighttime scene. Mahiki is part-owned by Guy Pelly, a former student at the Royal Agricultural College, Cirencester, who is often described in print as Prince Harry's "court jester", and was caught in the News of the World's drug "sting" on the prince during his teenage years.

Like all Sloane favourites, the club's prevailing atmosphere is fun rather than cool. "Toffs just want to have a laugh," says Mahiki's Piers Adam. "They want to take the piss out of each other. This place works because it's ironic. The bling crowd hate it. They come in and walk straight out again, because there's no smoke and mirrors, or Gucci and Prada."

Gucci and Prada would be an anathema to the princes. Their dress-code is scruffy and eclectic. "William and Harry's uniform comes from another age, and another cupboard," says the Sloane Ranger Handbook author Peter York. "It's mysterious: not speed-one hyper-Sloane, not even speed-two Johnny-Boden-Sloane. It's somewhere two rungs back from that."

Dylan Jones, the editor of GQ, has included both princes on both his best and worst-dressed lists. "One issue I would raise is that they lean towards Mario Testino type of photography," he says. "He tends towards the feminine and soft focus. I think they should harden themselves up. I would get David Bailey to do it."

A Bailey-type edginess prevails at London's most talked-about club, Boujis. This basement venue in South Kensington has also become a legendary fixture on the princes' social circuit, where they drink a shot called "crack baby" - a mixture of vodka, passion-fruit and champagne.

The club, which has a capacity of just 185, is full seven nights a week, thanks in no small part to its royal patronage. The prevailing atmosphere is of expensive debauchery, and its success is astounding. Boujis' parent company, Ignite, turned over £15m last year, and founder Matt Hermer expects to hit £25m next year.

"There is no doubt that the royal connection has helped us," he says. "Why do they come? Well, we have a reputation for not tipping off the tabloids if someone is inside. We've never done that, because I don't see the point. We try to be a home from home, where people can feel safe and comfortable."

Perhaps feeling safe and comfortable, especially when they've a Treasure Chest or Crack Baby in their hand, is all these two enigmatic young princes ever really wanted. s

Further reading Penny Junor's 'The Firm: the Troubled Life of the House of Windsor', is published by HarperCollins