A castle, a pig called Empress and a rather porky aristocrat

Timothy Spall goes posh in a new PG Wodehouse adaptation

To the manor born: Timothy Spall, Jack Farthing, Mark Williams and Jennifer Saunders

"Getting comedy right is very difficult indeed. It's like trying to make an immaculate cut-glass wine decanter," says Timothy Spall. "It has to amuse people while being beautifully shaped and at the same time a bit strange and barmy."

Spall is talking about his latest role, playing Lord Emsworth in the BBC's new take on P G Wodehouse's classic Blandings stories. Adapted for the screen by Guy Andrews (Lost in Austen) and set in 1929, the series about a family of unconventional aristocrats and their equally unorthodox servants aims to capture Wodehouse's tone of lovable eccentricity with a crack comic cast including Jennifer Saunders as Lord Emsworth's domineering sister, Connie, and David Walliams as his snooty secretary Rupert Baxter.

"With comedy, your aim is to please people, so if you're not managing to make them happy, they find it disproportionately disappointing", says Walliams, who very much looks the part of the imperious secretary in Baxter's little round spectacles, immaculate black three-piece suit, a gold watch chain across his stomach, stiff wing collar and impeccably smeared-down hair. "Comedy comes under greater scrutiny because viewers have much stronger feelings about what's funny than about what's dramatic. If people are trying to make you laugh and don't succeed, it's just really annoying. It just grates."

Blandings Castle, in reality Florence Court, a mid-18th century stately home in County Fermanagh, described by Andrews as "dysfunction junction", is the scene of a relentless battle between Lord Emsworth, known as Clarence, and his sister. He wants nothing more than to be left alone to spend time with his much-adored pig, The Empress. His only ally is his ever-loyal butler, Beach (Mark Williams). It's an archetypal comic clash between a lethargic, lazy bloke and an exasperated, efficient woman.

"There is an ingenue quality about Clarence," says Spall. "Even though he has massive responsibilities at the castle and finds his sister's bossiness a complete rectal ache, he remains one of the world's innocents. That's a very nice quality."

Saunders, 54, sitting in the make-up truck wearing a fetching plastic rain hood to protect her bouffant blonde wig from the elements, concurs that the characters are depicted not with sneers, but with sympathy. "Connie runs everything, and because she is much more able than he is, Clarence defers to her about everything – except his ruddy pig! But thanks to primogeniture, he still has the title. That means that Connie is in a rage all day long. Sometimes it's pure rage, but a lot of the time it's affectionate rage. She is actually something of a frustrated romantic. Despite all their differences, when they are threatened by outsiders, Connie and Clarence stick together as a family."

These lords and ladies from nearly a century ago may seem remote figures to us but Spall argues that there is a universality about them. "Wodehouse is saying that just because these people are aristocrats, it doesn't mean that they're not as frail and daft as the rest of us. Blandings works as a comedy because it juxtaposes these characters' supposed nobility with their ludicrousness and fallibility."

Contemporary audiences will find particular resonances in Blandings because during a recession we yearn to lose ourselves in a universe far, far away, thinks Spall. "Recession brings a great desire for nostalgia – hence the popularity of Downton Abbey. People romanticise the past. It's intriguing that during the Depression, Hollywood had its biggest ever success. Escapism always does incredibly well when times are hard."

Blandings should also score because of its parallels with modern-day society. "There is quite a lot of satire in this series which will strike a chord with viewers today," says Walliams. "There is still a lot of comedy about class in this country. Class still conditions us. It is still an issue that we have a prime minister and a chancellor who went to public school and Oxbridge."

"Twits are twits, and snobs are snobs. That endures wherever and whenever you are," adds Saunders. "It's a lovely little comedy with robust characters that could run and run. It's about human frailty and ambition. It doesn't have to do you good, or to mean anything. You can enjoy it for itself."

'Blandings' begins on Sunday at 6.30pm on BBC1