I avoided reading “The Guernsey Literary and Potato Peel Pie Society” because the title made me nauseous. It conjured up lethargic images of lacy ladies in their sixties surrounded by porcelain, tassels and Camomile, plodding earnestly through their tweedy book club’s latest novel. The blurb spoke of a cosy historical romantic Channel Island mystery (not another one) populated by people called Sidney and Dawsey and Amelia and I wondered how many readers’ had been reduced to gently contented bundles of treacly sludge before me.  I spotted a character called Ms Pribby, promptly put it down and never thought of it again.

But now, ten years after publication, Mary Ann Shaffer’s novel has become a cult phenomenon and spawned a film adaptation helmed by versatile and veteran director Mike Newell (Four Weddings and a Funeral, Harry Potter and the Goblet of Fire). This is a deceptively gargantuan undertaking as even the most zealous of the book’s fans (and there are many) would concede that the novel is not traditional fodder for blockbuster treatment.

The ‘action’ takes place predominantly on Guernsey in 1946, and follows the meeting of London author Juliet Ashton and Guernsey farmer Dawsey Adams after an extended period of correspondence. The two share a love of literature and Juliet is invited to attend the titular society, clandestinely created under Nazi-occupation, where she finds that the hangover of war is acute among the island’s neglected residents.

It all seemed ripe for ITV – a low budget period drama replete with dresses, drawls and Downton-esque whimsy and demanding the critical faculties of someone drifting in and out of a coma. When I heard that Lily James, an actor who has about  the range of Guernsey’s cultural exports, had been cast as the lead, the straight-to-TV vibe grew ever stronger.

And then I saw the film and was completely won over. Newell has crafted a tight, handsome and understated piece that flits between comedy and devastation with the finesse of the man who made ‘Prince of Persia’ and ‘Great Expectations’ within two years of each other.

There are two stories competing for attention – the superficial narrative of Juliet’s relationship with Dawsey (played with grim stolidity by Michiel Huisman), every beat of which is as sweetly predictable as Emma Bridgewater’s pottery – and the wider and more compelling portrait of the haggard periphery of the British Isles and its psyche, where troops with swastikas march past English cottages and collective identity is saturated in PTSD. It is a story seldom told and a World War far from the ravages of the Blitz.

While James herself competently plays a challenging part, the observer (a character whose name even the director forgot at the film’s screening), the other characters bristle with colour.

Penelope Wilton (Doctor Who, Shaun of the Dead)  playing an island resident whose daughter and granddaughter were killed in the occupation, is dazzling in her despair and delivers many of the film’s most powerfully anguished moments. Katherine Parkinson (The IT Crowd) plays a loopy bohemian whose mind has been dampened by too much of her own gin. She is genuinely very funny in a film that is not short on acerbic humour.

Guernsey itself is elegantly captured from dawn to dusk, forest to ocean. The film was actually shot in Devon and Cornwall on account of Guernsey being full of Co-ops and tax avoiders’ penthouses, which reportedly left Guernsey folk frothing and fuming in bewildered antipathy. Nevertheless, the south west coast is ravishing – crinkled cliffs dusted with chalk are blasted by rich, swollen waters and coal-grey cottages cling determinedly to hillsides. It feels like an appropriate setting for a story rooted in people’s simmering trauma and stoic resolve, a wild and windy kingdom of neglect.

‘The Guernsey Literary and Potato Peel Pie Society’ knows exactly what it is – an enormously capable and charming little film that succeeds admirably more often than not and, unlike its title, doesn’t outstay its welcome. It is aptly the cinematic equivalent of pie – warm, comfortable and meaty, and if not thrilling, honest.

The Guernsey Literary and Potato Peel Pie Society is on general release in UK cinemas on 20th April