The Aristocrats: inside the lives of the irredeemably posh

"I planted that copper beech in 1980," says the Marquess of Blandford, pointing at a copper beech. "Those were wild times, eh?" enthuses the interviewer in The Aristocrats: Blenheim Palace (Thursday, 9pm, C4). "Yeaaah," drawls the marquess, wistfully. "That's probably why it's got a curious lean to it."

Poor the Marquess of Blandford. It's not easy forging a future as the heir to one of Britain's grandest stately homes when your present is up to its cravat in the past. The marquess – AKA Jamie Blandford, AKA notorious, rambunctious, formerly disgraced and once nearly disinherited heir apparent to the dukedom of Marlborough – is the cheeringly gristly knot at the heart of the first episode of The Aristocrats, a sprightly new two-parter that takes a surprisingly even-handed gander at the lives of the monumentally privileged as they yah and blah around their often endangered country piles.

Once a thorn in the side of modern toffdom – the string of minor convictions, the stints in rehab, the unbecoming leisurewear, the infamous legal spat with Daddy – Jamie is now, at 56, a reformed, drug-free and endearingly blustery galumpher with Wurzelian hair and skin the colour of raw mince. He looks like Rick Wakeman at his own wake. Or a retired surfer running a pocket bong concession out of a campervan at Taunton Deane services. He is ambivalent about his inheritance, quietly miffed at the involvement of the board of trustees brought in by his family to oversee his behaviour, and perfectly happy leaving his father to what the narrator refers to, wryly, as "the small print of Blenheim's existence".

Now 86, Daddy – the 11th Duke of Marlborough - has the garbled, sticky plum crumble diction of the irredeemably posh. "Weaurgh," he says testily of a £1.75m plan to restructure Blenheim's dam. "Gnyarr urph health and safety weaurgh." When he's not pebbledashing the screen with peevish vowels the duke – AKA John Spencer-Churchill, AKA, bewilderingly, "Sunny" – spends his time power-walking along staggeringly ornate corridors, a maddeningly elusive blur of industry and corduroy. On the rare occasions we manage to catch up with him, we find ourselves peering into the sort of face you usually find on banknotes: brisk moustache, chin like a fleshy landslide, eyes so piercing they could blow up the east courtyard's unfinished multi-million-pound toilet block.

But! But, but but. We want to ask the duke about his relationship with Jamie and the circumstances that led to their reconciliation. We want to ask him about his three ex-wives, the future of the aristocracy, and whether he has days where he'd like to throw his titles in the dam and bog off to live with the Chacma baboons of Mozambique. We imagine that Jamie and The Aristocrats probably do, too. But we don't get the chance because he's off again, brushing aside the camera crew and actioning change with a stately swipe of his feather duster ("Eurk … don't like this table … nyarrph"). Not that we'd expect much in the way of explosive revelation, mind. Blenheim Palace isn't that sort of place. It is not Fun House with Pat Sharp. The Duke almost smiling as he says "Got to keep going – best foot forward!" is about as partytimes as it gets.

Of course, it could be different behind closed doors. Perhaps the 11th Duke of Marlborough makes balloon animals for visiting dignitaries. Perhaps he does Esther Rantzen impressions in the bath. We may never know. This world is essentially impenetrable, concedes The Aristocrats, pressing its nose against an east wing window only to find the entire household has gone out to buy a new fish knife. There's a sense of generations passing in a haze of crisp formalities, with decades of unexpressed emotions left to accumulate, like dust on a snoozing duchess. But then we meet Jamie at a polo match and realise that, to be honest, this reticence lark is probably for the best.

"Do I bet?" he bellows over the thud of privileged hooves. "Oh no. Bookies hate me. Jewish blood. Hyurr-hyurr!" Father, forgive them, for they know not what they do.