The Guernsey Literary and Potato Peel Pie Society: as bland as mashed potatoes

After shaking off the landslide of mediocrity that is The Guernsey Blah Blah Blah Blahdy Blah, I felt the urge to watch Their Finest – last year's underrated UK wartime gem – five or six times to cleanse the tweeness from my sugar-rushed brain.

Adapted from some book or other, the film plays like an acidic parody of all that's bad about British heritage film-making. At least two Downton Abbey alumni (Lily James and Jessica Brown Findlay) join at least one theatrical great (Penelope Wilton) and at least one graduate of the British new wave (Tom Courtenay) in a film that pays more attention to the cut of the actors' tweed than to narrative cohesion.

Good actors turn bad. Bad actors turn worse. It’s pretty. It’s polite. It’s so anaemic you feel the urge to feed it a pint of Guinness.

To be fair, the screenwriters have been presented with a genuine quandary. Much of Mary Ann Shaffer and Annie Barrows's novel is told in epistolary fashion.

In post-war London, Juliet Ashton (James), a young writer of biographies and popular fiction, receives a letter from a Guernsey farmer (Michiel Huisman) who is looking for a copy of Lambs' Tales from Shakespeare. A correspondence develops that moves towards the origins of (clear some space for the full title) the Guernsey Literary and Potato Peel Pie Society.

During the Nazi occupation, locals invented the book club to explain their nocturnal meetings. We hear of resistance, betrayal and mysterious births.

On screen, the wartime episodes play out in a series of hurried flashbacks that allow little space for character development. Brown Findlay's brave resistance figure is, in particular, hopelessly lost in the shimmying from past to present. Conversations in the book club feel anachronistic and forced. The supposed tension between Juliet's three potential suitors is undermined by the milky blandness of the two that aren't the always-welcome Matthew Goode.

Glen Powell, as a visiting GI, has no distinguishing characteristics aside from his generic American confidence. Huisman's dullness is of another class altogether. Have I seen him before? It's hard to tell. I could have shared a cell with this guy for six months and forgotten he ever existed.

For fans of the novel only.