Downton Abbey: A touch of class

It wasn't the kind of weather that you imagine for a visit to Downton Abbey – as played on television by Highclere Castle on the Berkshire-Hampshire border. This was no Edwardian-style summer's day, deep shadows on the manicured lawns and all that – instead, a bank of low pressure pushed squally rain up the M4 corridor. But then, the dark clouds had been gathering for the aristocratic Crawley family and their servants – and for the 13 million of us following their exploits – since the first series of the ITV drama ended in December with the Earl of Grantham (Hugh Bonneville) taking that telephone call with the news that Great Britain was at war with Germany.

The lamps may have been going out all over Europe, to borrow and adapt Foreign Secretary Sir Edward Grey's phrase from August 1914, but television sets have been going on across the world since Julian Fellowes' costume drama became the television phenomenon of last year. Downton Abbey has gone global, selling to more than 100 countries and, recently, securing three Emmy nominations. Fans include the Duke and Duchess of Cambridge and Joanna Lumley, who pestered Fellowes to write her a cameo.

After driving over a bridge across the busy A34 from Newbury to Southampton, you are suddenly in a different era – a secluded idyll with sheep grazing on Capability Brown parkland that probably contains more cedars of Lebanon than they have in Lebanon. The famous castellated turret makes itself known over the brow of a hillock. Such a magical effect for any fan of the series is only spoilt by the lorries, marquees and catering trucks that are clustered in front of the house. Filming is in progress.

I am joined by Fiona from the Melbourne Herald Sun. "It's compelling," she says, "you can binge on it. And Dame Maggie Smith... her words have become aphorisms." It is not Smith that I spot on the gravel driveway, however, but Bonneville, a parka over his Edwardian formal wear, trying to keep the rain out as he sips coffee from a polystyrene cup.

"We've just come out of the war and now we're facing Spanish flu," he explains, helpfully, before being whisked away to shoot a supper scene from the eighth and final episode (not counting a Christmas special) of the forthcoming series.

This is taking place in Highclere's state dining room, so Fiona and I step over the crested doormat (Highclere belongs to the Earl of Carnarvon, who has wisely gone racing for the day), through the Victorian Gothic hallway – redesigned, like the rest of the house, by Sir Charles Barry after he had finished with the Houses of Parliament – and into the panelled dining room. Seated around the table, waiting for the call to action while peering into plates of what looks like Brown Windsor soup, are Bonneville; Elizabeth McGovern (Lady Cora, the American heiress married to the Earl); Maggie Smith (Violet, Cora's mother-in-law from hell – the Dowager Duchess of Grantham); Penelope Wilton (Violet's sparring partner, Isobel Crawley); Michelle Dockery (Lady Mary); and Dan Stevens (Lady Mary's true love, Matthew Crawley). Staring disdainfully down at this grouping, I am rather surprised to see, is an enormous equestrian portrait of Charles I, by Van Dyke. I hope the Carnarvons have good household contents insurance.

In the new series, Downton has been turned into a convalescent home – the daughters of the house becoming lorry drivers, nurses and suchlike. But my quest, apart from having a snoop round, is less to give away plots from the second series than to pinpoint the appeal of the first. I was not an immediate fan – frankly, Downton Abbey seemed a bit clumsy for a viewer raised on the meticulous standards of BBC period drama. Hilariously unsubtle at times, in fact. The series grew on me – albeit never to the point of infatuation – but it turned out that I couldn't have chosen a better confidante than McGovern.

"I'm probably more of a Cranford man," I admit.

"That's all right," she coos back. "My husband directed Cranford". Lucky break. McGovern, an American who in the 1980s turned her back on a Hollywood career, is married to the director Simon Curtis.

The sun having emerged, McGovern, in Lady Cora's black velvet dress but with her hair protected beneath an unflattering net, is sitting on a chair on the front lawn, reading an Edith Wharton paperback. "Terrible way to make a living, isn't it," she smiles.

How does she explain the success of Downton Abbey?

"People find it relaxing," she says. "My contemporary brain finds it very relaxing, looking at an age when everybody knows how to behave because the rules are very clear. There's something very stressful about today's world, when people are allowed to behave how they want. You're always having to make these choices and judgement calls about how to behave, whereas in the world of Downton Abbey everybody knows what's expected of them."

Up to a point, Lady Cora. In Fellowes' script, there seems rather too much informality between upstairs and downstairs. But I get her point.

McGovern adds: "Also, a lot of times I turn on the TV and the drama is so heightened beyond reality. It's like people are striving to outdo everyone else with that frenzy. By contrast there was one scene in Downton Abbey last year where the entire scene was me and Isabelle and my mother-in-law discussing the best way to find a lady's maid. It's the detail people like."

Ah, the details. Downton Abbey became a bit of a laughing stock last autumn when, in one shot, a television aerial was spotted. Other viewers claimed to notice a car from 1921, a modern street sign, someone playing "After You've Gone" on the piano – it was not written until 1918 – and double yellow lines in a scene set in a village street.

"There aren't any double yellow lines in Bampton [the Oxfordshire village that stands in for Downton]," says the series producer, Nigel Marchant. The TV aerial existed, however. "You watch the show so many different times – so many different cuts and forms, grades and everything else – and there's always something," he allows.

Fellowes, who is planning a "nit-pick of the week award" for the new series, hit back: "The real problem is with people who are insecure socially, and they think to show how smart they are by picking holes in the programme to promote their own poshness and to show that their knowledge is greater than your knowledge."

Back on set, everything shuts down for lunch. Does Dame Maggie Smith partake of the catering, I wonder aloud. Fiona contorts her face and nods over my shoulder, for Dame Maggie has stepped out of a chauffeur-driven Bentley, hair in a net like the other actresses. If there is royalty here at Highclere it is Smith, who will not, we are told, be speaking to journalists. The younger actors are more forthcoming, including Michelle Dockery and Laura Carmichael, who play the antagonistic sisters Lady Mary and Lady Edith. What did they think was at the root of the show's success?

"Even though it's something that feels otherworldly in its date and period, it's just a workplace drama," says Carmichael, insightfully. "Also, Julian writes so well and does a fantastic job of keeping so many characters' stories in the air."

Dockery believes Downton Abbey has the advantage that, unlike most costume dramas, it is not based on a classic book. "So there's nothing to compare it to," she says.

Whatever its causes, the "Downton factor" is good for the ITV share price and healthy for local tourism. The number of coach parties visiting Highclere has quadrupled and un-official Downton tours have sprung up. Paparazzi have taken to hiding in the rhododendrons, seeking sneak snapshots of the cast. One tried to disguise himself by putting a fire warden sign on top of his car; another, in full camouflage army gear, was apparently flushed out by Lady Carnarvon.

This rhododendron is the hiding place that was used by photographers in 2005, when Katie Price and Peter Andre's wedding was held at Highclere. Apparently, Price's dress was so voluminous that she couldn't fit through the library doors. The library, which is next door to a room which doubled for the boudoir in which Lady Mary was seduced by a Turkish diplomat, is full of books that look like they haven't been read since Queen Victoria's reign; metres and metres of biographies of long-forgotten aristocrats.

Four volumes of Lord Brougham's speeches anyone? Or The History of the Helvetic Conference? Thank heavens for television. Thank heavens for Downton Abbey.

'Downton Abbey' returns to ITV1 in September