Dir: Lone Scherfig

With: Gemma Arterton, Sam Claflin, Bill Nighy

Runtime: 117 minutes

THERE are certain actors whose arrival on a cinema screen prompts a palpable reaction in audiences. You can almost hear the sighs of relief and see shoulders relax as the collective thought ripples through the stalls like a mental Mexican wave. “Well, whatever this carry on turns out to be,” the hive mind buzzes, “the evening won’t be completely wasted now that X has turned up.”

I’ve seen Denzel Washington do it many times in the US, ditto Tom Hanks and Meryl Streep. In Scotland, it’s James McAvoy who has national cinema treasure status. But for the UK as a whole, it would be hard to beat Bill Nighy (a half stake in whom Scotland can claim since his mother, a nurse, was from Glasgow). True to form, the louche, dapper and leonine star of The Best Exotic Marigold Hotel is the best thing in Lone Scherfig’s congenial wartime comedy drama Their Finest.

Gemma Arterton plays Catrin Cole, a young woman living in 1940 London who is taken on by the Ministry of Information as a film writer. As the war starts to hit hard on the home front, the Ministry is called upon to crank out ever more cheerful and spirit-lifting films. The immediate task for Cole’s unit, led by arrogant young director Tom Buckley (Sam Claflin), is to make a feature film about the Dunkirk landings that will show Britain in the pluckiest possible light.

Cole picks up on a local paper story about two sisters being among the many who ventured out in small boats across the Channel to evacuate British soldiers. Thinking this would make the perfect plot, she interviews the pair, only to discover the story is not as straightforward as it seems. But hey ho, this is the motion picture business. Films, Buckley tells her, are just “real life with the boring bits cut out”, the boring bit in this instance being large chunks of the truth.

As if heeding Buckley’s words, Scherfig, the director of An Education and One Day, wastes no time in cracking on with the jolliest part of the story – the making of the film itself. It is here we meet the magnificent Ambrose Hilliard (Nighy), a thespian so hammy he could feed a small town for a month. Ageing, spectacularly vain and acutely aware of his diminishing status in a business that is never kind to sensitive souls, Ambrose is part monster, part angel: a funny, warm delight when he wants to be, a whiny nightmare when unhappy.

Scherfig, adapting Lissa Evans’s novel Their Finest Hour and a Half, has a ball recreating the shoot, with the cast taking their cue from her. There are few enterprises more ridiculous than filmmaking, which is essentially adults playing at dress-up in front of cameras, and Their Finest has plenty of good-natured, loving jokes at the profession’s expense. But we also see that film, much like war but without the casualties, is a communal event, a family affair, where every sinew is strained to the same end.

The film hits the odd sticky patch when it seems to suddenly remember that war is not a funny business at all. It is understandable why it should do so, but the effect on the tone can be jarring. One minute we are deep in a Dad’s Army style caper, chuckling away at the daft humour, the next we are pulled up short by tragic reality. There is also a love triangle going on, which adds to the all-over-the-shop tone.

If you can put that to one side, there is a lot to enjoy in Scherfig’s piece. Its love of film as an epically silly but life-enhancing endeavour, and its affection for the characters, shine through. Nighy is terrific, but then you expect that. But closely following him is Arterton, playing the woman taken on to write “the slop” – the gooey, lovey-dovey material – but who turns out to have so much more to offer. Like character, like actor, Arterton is rapidly advancing towards national treasure status in her own right.