Wife Sam also said to be at ease partying with high-fliers in the Cotswolds

Prime Minister said to let his hair down at events for Oxfordshire's wealthy

From a giant marquee in the grounds of a honeycomb-coloured Cotswold farm, thudding music reverberates into the night.

Blacked-out Range Rovers — the vehicle of choice for west Oxfordshire’s wealthy — are spread across a field like a row of small tanks, dwarfing the sleek limousines and the sports cars with personalised number plates.

Under the black sky, shadowy figures are pulling on cigarettes. These are the chauffeurs, who are bracing themselves for a long night in Sarsden, epicentre of the infamous Chipping Norton set — rich Londoners who have weekend homes in the Cotswolds.

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Riding out before the hunting ban: In a rare and exclusive picture, David Cameron (pictured centre) with the Heythrop Hunt in December 2004

Close: The PM chats to TV host Jeremy Clarkson and former Blur bassist-turned-farmer Alex James during an event in Kingham, Oxfordshire. The trio are well-acquainted as part of the infamous 'Chipping Norton set'

Inside the marquee, more than 500 of the wealthiest and most powerful people in Britain are seeing in the New Year in style. The Moroccan-themed tent is festooned with floor cushions. Beautiful people lie draped over pouffes, sipping drinks by flickering lamp light.

The year is 2008. This is the annual New Year bash for ‘the set’, a party so exclusive and impenetrable by the paparazzi that the many well-known guests feel able to relax. Whatever happens in the marquee will stay in the marquee, because nobody in this gilded circle would risk ostracism by breaking the omerta that governs their social gatherings.

The guest list is tightly controlled by the stars of the set: TV host Jeremy Clarkson; former Blur bassist-turned-farmer Alex James and his wife Claire Neate; racehorse trainer Charlie Brooks and his glamorous sister Annabel; and the queen bee of them all: Rupert Murdoch’s protégée Rebekah Wade — now known by her married name Brooks.

Whenever anyone new is invited to one of these gatherings, their name requires the approval of all. Among the guests tonight is David Cameron, Leader of the Opposition, and his wife Samantha, who live a mile or two away in the hamlet of Dean.

Also there are Shadow Chancellor George Osborne and his wife Frances; Andy Coulson, former News of the World editor; BBC executive Alan Yentob and the director-general Mark Thompson.

By the time the PR Matthew Freud and his wife, Rupert Murdoch’s daughter Elisabeth, sweep in, the party is in full swing — loud, boozy and perhaps not entirely free of class-A drugs.

Whether fairly or unfairly, social gatherings among the upper echelons of society in these parts have acquired a reputation for featuring narcotics. So much so that some affectionately dub Chipping Norton ‘Chipping Snorton’.

As the clock approaches midnight, guests in varying condition troop out of the marquee to watch a spectacular firework display. Many seem euphoric, including Mrs Cameron. In the small hours of New Year’s Day, she drags on a cigarette and gives it her all on the dance floor.

Revelations: The new insight into the Prime Minister's life has emerged in the new book, Call Me Dave: The Unauthorised Biography of David Cameron written by Lord Michael Ashcroft and Isabel Oakeshott

Friends: Racehorse trainer Charlie Brooks and his wife Rebekah Brooks are among those deemed to be in the 'Chipping Norton set' - the wealthy Londoners who retreat to the Cotswolds

Also present that night was a former newspaper executive, well used to scenes of excess, who recalled being shocked by the sheer concentration of power and money.

‘It was incredible to see all these people letting their hair down,’ he said. ‘But something felt wrong. There were just too many people in too many powerful positions too close to each other. I remember saying to the person I was with: “This will end in tears.” It wasn’t right.’

Emerging from the loos later that evening, the former newsman, a working-class boy made good, bumped into Cameron. ‘You’re not one of us, are you?’ the Leader of the Opposition quipped cheerfully.

The guest was left wondering if it was a reference to his politics, his social status — or both.

It is at such exclusive social occasions, in his constituency in Witney, that David Cameron can really be himself. In manor houses, converted barns, farmhouses and stately homes belonging to friends, the Prime Minister kicks off his shoes and lets his guard down. Details of these parties rarely leak. Members of the gilded circle generally have a strong interest in keeping their mouths shut about what they get up to behind closed doors.

[Jeremy] Clarkson’s opening line to Dave was: "Come on; let’s face it, no one in this tent could care less about comprehensive schools. What they want to know is why organic milk is so expensive at Daylesford?" Anonymous guest at Conservative Party fundraiser

Theirs is a world of helicopters, domestic staff, summers in St Tropez and fine food from Daylesford — the organic farm shop owned by Lady Carole Bamford, wife of billionaire industrialist and Cameron supporter Sir Anthony Bamford.

The Camerons dip in and out of this social scene, aware that too close an association with it might cause political damage.

At one late-night party, according to a member of the Chipping Norton set, Cameron became so inebriated that he lost his mobile phone.

‘He was wandering around drunk, asking if anyone had seen it. I couldn’t believe it,’ says the guest. When she feels as if she’s in safe company, Samantha herself can be extraordinarily indiscreet. At another private party, she regaled guests with a colourful account of how she and Cameron became so intoxicated on holiday in Morocco that they vomited.

One function they both attended was a Conservative Party fundraiser — held at the Georgian stately home of Cameron’s friend and neighbour Lord Chadlington.

According to one guest we spoke to: ‘There was a huge marquee full of ladies with big hair and even bigger jewellery. The entertainment for the evening was Dave in conversation with Jeremy Clarkson, who seemed to be smashed off his face. There was a lot of drink around. David was loving the whole laddishness of it. He was really playing up.

‘Clarkson’s opening line to Dave was: “Come on; let’s face it, no one in this tent could care less about comprehensive schools. What they want to know is why organic milk is so expensive at Daylesford?”

‘David tried to bluster his way out of it, but Clarkson just went on, saying things like: “Seriously, Dave, everyone sends their kids to private schools . . .” ’

Having fun: Despite the book Mr Cameron was in high spirits at a reception at Downing Street last night tonight where he celebrated England's recent Ashes win with the nation's men and women's cricket team

Mr Cameron welcomed England's cricket stars to Downing Street just hours after meeting the Danish PM

Such incidents, of course, play directly into the hands of Cameron’s political opponents, who caricature him as an Old Etonian ‘toff’, most at ease among the super-wealthy and hopelessly privileged and out-of-touch.

It is a stereotype that Cameron painstakingly avoids reinforcing in public, though he appears to live up to it behind closed doors.

He was so anxious to avoid being seen in tails at the wedding of Prince William and Kate Middleton, for instance, that he toyed with the idea of wearing a normal suit. And he initially baulked at sending a signed photograph to Eton for inclusion in its gallery of Old Etonian Prime Ministers. Undoubtedly, the private David Cameron feels at home with some of the very wealthy and louche characters of the Chipping Norton set. But that is only part of the picture.

Cameron’s life may be a tale of privilege, but his rise to the premiership is the result of some remarkable qualities — not least an unflinching self-belief, a well-balanced character and a rare political ability to attract many of those who wouldn’t normally vote Tory.

From the moment he presented himself as a prospective Tory candidate to the Witney Conservatives — he seemed a perfect fit.

They may not have dreamed he could become Prime Minister — but they warmed to the attractive, well-spoken Old Etonian who had impeccable Tory connections and told them exactly what they wanted to hear.

And if he seemed a little ‘square’ to some of the loucher members of the Chipping Norton social set, his power and his beautiful hippy-chick wife soon gave him an entrée.

Tally-ho Cameron and the hunt chum he helped

Journalists have long sought a picture of hunt supporter David Cameron riding to hounds, to no avail — prompting suspicions that someone with Cameron’s interests at heart may have paid to take any such images off the market.

But after extensive inquiries, we finally uncovered this photograph of the future PM preparing to set off for a day’s sport.

It was taken at the final gathering of the Heythrop Hunt before the ban came into effect, a few days after Christmas 2004. Cameron can be seen on a fine bay mount, looking a little nervous, as horses assemble in the square in Chipping Norton.

Every year, in the lull between Christmas and New Year, the Heythrop Hunt meets a few miles from Cameron’s constituency home. They assemble at Cornbury Park, a stately home which provides a spectacular backdrop for the horses and hounds. The estate belongs to friends of the Prime Minister, and many of his social set are involved in the annual meet.

Mr Cameron is pictured at the Heythrop Hunt before the ban came into effect, a few days after Christmas 2004

Watching the hunt thunder off over the fields is an unforgettable sight, but Cameron dares not be there himself any more. Since becoming Prime Minister, he’s avoided being seen at hunts, let alone being photographed on horseback. Given the associations of equestrianism with class and privilege, he believes it’s too toxic.

Yet he’s an avid supporter of hunting, and does what he can to help hunts and huntsmen behind the scenes. He loves rural life and wants to protect its traditions: it is a world he grew up with and understands.

‘He can scratch a pig’s back so effectively that the creature sighs,’ said a journalist who saw him do this in the Cotswolds. Cameron told the same journalist that he could ‘castrate a ram with a pair of pliers’.

The last time he’s widely known to have gone hunting is in January 2003, when he went out with the Heythrop. Afterwards, he wrote a piece for the Guardian which implied it was his first time. (‘Nothing had prepared me for the sheer terror of a day’s hunting,’ and so on.)

It would be surprising if this were his first hunt. His old friend Bruce Anderson says Cameron used to joke that the ‘terrible thing about the Hunting Bill is that only two people are affected by it: Prince Charles and me’ — suggesting it was a regular hobby.

Guy Avis, his next-door neighbour in the Cotswolds, is honorary secretary of the Heythrop, and says Cameron has the use of a mount stabled at the nearby village of Ginge.

The hunting ban finally came into force in 2005. Far from dying out, however, the sport is booming, mostly in the form of trail hunting, in which hounds pursue an artificially laid scent.

Yet ‘accidents’ happen, when hounds ferret out real foxes that are pursued in the same way as they have been for hundreds of years. The Heythrop has been involved in a number of court cases relating to this.

While Cameron was Leader of the Opposition, his friend Julian Barnfield, a professional huntsman with the Heythrop, was charged with various offences of hunting a fox. The case was later dropped on a technicality.

After spending hours fending off questions over lurid claims he violated a dead pig's head yesterday, the Prime Minister last night welcomed Danish Prime Minister Lars Loekke Rasmussen to Downing Street (above)

Cameron, we discovered, intervened personally, writing to the Attorney General on Barnfield’s behalf in June 2008.

Later, Chris Edgell, a former detective constable involved in the case, tried to obtain a copy of the letter using the Freedom of Information Act, but his application was rejected.

Cameron’s constituency office also refused to provide Edgell with a copy of the correspondence — on the basis it followed ‘a private meeting between a constituent and his MP’. Did the police and Crown Prosecution Service (CPS) go easy on Barnfield after pressure from Cameron? It seems more than possible.

Edgell says: ‘I have learned from CPS and police sources that Cameron’s letter to the Attorney General was sent on to CPS headquarters, who sent it on to Thames Valley CPS, who then sent it to Gloucester CPS, who then sent it on to the Complex Case Unit at Bristol, where barrister Kerry Barker dealt with it.

‘I saw the letter. It said something like: “Is this really a productive use of police time?” ’

Revealed: The PM's brother is 'family' to Rebekah

Before Christmas last year, David Cameron accepted an invitation to a carol service that led to an awkward encounter. The host was his neighbour, property tycoon Tony Gallagher, who has a private chapel attached to his stately home near Chipping Norton.

In the flickering candlelight, Cameron may not immediately have noticed his one-time friend and confidante Rebekah Brooks, the former chief executive of News International — owners of The Times and the Sun — sitting quietly in one of the pews with her husband Charlie. Her trademark tumbling red hair was tucked under a hat.

Though neighbours, Cameron and Brooks had taken pains to avoid crossing paths in the three years since her arrest for alleged corruption and phone-hacking in July 2011. Now they were just a few feet apart — and their host ensured they couldn’t pretend otherwise.

Friendly: Mr Cameron and newspaper boss Rebekah Brooks (pictured) were once good friends as revealed during the Leveson Inquiry, which revealed how often they texted and emailed

Wrapping up the service, Gallagher offered an unusual benediction: ‘Let us give thanks that Rebekah and Charlie are with us this evening.’ He didn’t need to spell out where else the couple might have been — behind bars.

Neither Cameron nor Brooks knew how to react. Embarrassed, she turned and half smiled at him, shrugging and raising her palms heavenward.

The phone-hacking affair was the most serious crisis of Cameron’s leadership, culminating in the imprisonment of his former communications chief Andy Coulson and criminal charges against two of his close friends: the Brookses.

The decisions he made at the height of the furore triggered a year-long legal inquiry which turned former allies into enemies; exposed uncomfortable details of his dealings with the media; and was a hugely time-consuming distraction.

Not only did the affair raise serious questions over his judgment, but it was also a source of acute personal embarrassment, detonating a bomb under the Chipping Norton set. Naturally, attention focused on the shattering of his relationship with Brooks, but there was another player in the drama: Cameron’s older brother Alex.

Changes: The PM was once good friends with Rebekah Wade, now known by her married name Brooks, but they are only now on speaking terms in the wake of her arrest for alleged corruption and phone-hacking

Racehorse trainer Charlie Brooks had been at Eton with Alex Cameron, a successful QC, and the two men were exceptionally close. After the then Rebekah Wade met Brooks, marrying him in 2009, she was often at his farm just three miles from David Cameron’s home.

After that, it was natural all the couples would socialise — Alex and Sarah Cameron; David and Samantha Cameron; and Rebekah and Charlie Brooks.

But it was Cameron’s brother who remained steadfast when the phone-hacking scandal erupted. He refused to abandon his old friends.

At a risk of causing acute embarrassment for the Prime Minister, Alex and his wife continued seeing the couple throughout the long, drawn-out criminal proceedings against them. They treated Brooks and her husband as if nothing had changed — even going on holiday together during a break in the trial. The Brookses consider Alex ‘family’. The PM is not in the same bracket.

There can be no doubt, however, that Brooks was once close to David Cameron. Since the early days of his leadership, she had been generous with her contacts and advice. In the run-up to the 2010 election, Brooks had also thrown News International’s weight behind the Tory campaign.

Yet from the moment she and her husband were arrested, the Prime Minister deserted them, terrified of the political implications of being seen in their company. She expected and needed his support — or at least his silence. Instead, he threw her to the wolves, saying if he were in charge of News International, he would have accepted her resignation.

Cameron’s betrayal was devastating. Samantha tried to soften the blow by sending conciliatory messages through intermediaries in a shop in Chipping Norton — but for a long period, Brooks was deeply angry.

On top of that, Cameron set up the Leveson Inquiry to investigate the culture, practices and ethics of the Press. Having agreed to appear at it for questioning, he’d then undergone months of painstaking preparation.

Even so, when he took the stand in June 2012, embarrassing details came tumbling out. Not just his 26 meetings with News International executives in 15 months, at a time when the company was focused on taking full ownership of Sky (NI’s parent company News Corp owned 39 per cent), but his frequent exchanges of texts with Brooks.

Among those she’d sent him was a particularly toe-curling one, just before the party conference in 2009. It began by sympathising with the PM over an ‘issue with The Times’ — most likely a hostile article — and suggested she could placate him over ‘country supper soon’.

The message continued: ‘As always Sam was wonderful (and I thought it was OE’s [Old Etonians] that were charm personified!). I am so rooting for you tomorrow not just as a proud friend but because professionally we’re definitely in this together! Speech of your life? Yes, he Cam!’

Their relationship raised uncomfortable questions about News International’s support for the Tories — and whether the company expected something in return.

Lord Justice Leveson later concluded there was no evidence of a secret deal, but he was sharply critical of the ‘particular kind of lobbying out of the public eye’ between senior politicians and the Press.

Row: The astonishing claims made by Lord Michael Ashcroft (pictured with the Prime Minister) are said by friends of Mr Cameron to have been motivated by revenge

Industry insiders claim the way Brooks used to talk privately about her relationship with Cameron fuelled suspicions she had him in her pocket. One source claims she brandished a text message from him over dinner to illustrate the closeness of their friendship. The other guests were colleagues from other newspaper groups, all of whom were campaigning against News Corp boss Rupert Murdoch’s bid to take over Sky.

One of the guests claims: ‘The text said something like: “Looking forward to supper at the weekend. Love David xx.” She then said words to the effect of: “I don’t know why you’re even bothering to run this campaign, because this is a done deal.” That was typical of Rebekah and the way she conducted the whole Sky thing. As chief executive, she had become chief lobbyist. Her job by that stage was entirely about lobbying.’

Brooks denies showing such a text.

On June 24, 2014, she and her husband were dramatically cleared by a jury at the Old Bailey. It marked the end of a three-year ordeal, during which they’d lost their reputations and some of their friends.

Today, Cameron and Brooks are back on speaking terms — but only just. There are no cosy suppers, no horse rides together, no intimate soirées with friends.

Although Samantha invited the couple to her birthday party at Chequers last year, they didn’t feel it would be right to accept. Torn apart by the phone-hacking saga and the divorce of several of its leading lights (Elisabeth Murdoch and Matthew Freud; Jeremy Clarkson and wife Frances), the Chipping Norton set last year came up with an ironic new name: ‘The Upset’.

Brooks has told friends that she understands why Cameron reacted as he did. She likes to relate a fable about a scorpion and a turtle she heard from Peter Mandelson.

‘The scorpion wants to cross a river, and asks the turtle for a ride. The turtle refuses, fearing he will be stung. The scorpion argues that stinging the turtle would not be in his interests, because they will both drown. So the turtle agrees to give him the ride.