Lone Scherfig’s entertaining and insightful romantic drama, Their Finest, is set during the Blitz in 1940. This was the beginning of one of the richest and most contradictory periods in British film history.

In 1939, it had looked as if British filmmaking was going to grind to a halt and that cinemas would be closed down for the duration. Even when they re-opened, production levels plummeted. Nonetheless, against the odds and as the bombs fell on London, the war years turned out to be an extraordinarily fertile period – a mini golden era in which old attitudes about gender and class were turned on their head. The Government may have been using filmmaking for propaganda purposes but exceptional work was done all the same. Audiences clamoured for new movies that reflected the realities of their wartimes lives rather than for star-filled Hollywood fantasies.

The film opens with footage from a documentary of the period showing women in a factory. One tells her supervisor that she has had some bad news: her man has gone missing. She then adds with an absurdly British understatement, in the face of bereavement and death, that she will feel much better when she has had “a cup of tea”.

The footage is greeted by audiences with catcalls and derision – as an example of patronising filmmakers having no clue how to depict working class women on screen. This is where Catrin Cole (Gemma Arterton) comes in. She is a young Welsh woman who has been working as a copywriter, based on a real-life screenwriter, Diana Morgan, the only female writer on contract at Ealing Studios under notoriously chauvinistic boss Michael Balcon. She is hired because the film studio bosses need someone who can write the “slop” (the “girl talk”) and “cultivate a more convincing female angle”.

Catrin thinks she is being taken on as a secretary and is startled to discover that actually she is there to work on the screenplays. Her job is help provide a script that is authentic, optimistic. . . and that has a dog (always good for morale) for good measure.

Arterton gives a well-judged and engaging performance as Catrin, capturing her character’s mix of naivety and ambition, fieriness and diffidence. Catrin is clearly talented but has to work out just how much independence she is allowed to show. She is paid far less than the men for doing the same job and is relentlessly condescended to by them – but they are dependent on her.

So is her ne’er do well war artist husband Ellis (Jack Huston). He has been disowned by his family because of his politics. He may be a destitute radical but when it comes to domestic arrangements, he wants his wife to stay at home and defer to him.

Their Finest Trailer

Adapted from the Lissa Evans novel Their Finest Hour And A Half, this is a self-reflexive affair – a film about filmmaking. Catrin is assigned to research an uplifting story that her bosses in the Ministry of Information think will appeal on the home front, to women in particular. The story in question is about two sisters who defied their drunken sea captain father, borrowed his boat and headed to Dunkirk to help in the evacuation of the stranded allied forces.

In reality, the boat had engine trouble and didn’t make it to Dunkirk. The reports in the local papers about the sisters’ heroism were wildly exaggerated. Nonetheless, once the story is given the Technicolor treatment and is written up by Catrin and her colleagues, it becomes rousing fare for cinema goers.

One of the pleasures of the film is the way it both gently mocks and celebrates the British in wartime. At times, the Brits can seem very absurd indeed. Among the main characters here is the ageing actor Ambrose Hilliard (Bill Nighy), a narcissistic old-timer who was once a matinee idol. Nighy plays him in wonderfully haughty and conceited fashion.

Ambrose is in his 60s and simply can’t accept that he is no longer top of the bill – or that all the best Italian waiters at his favourite Soho restaurants have been interned as enemy aliens. He treats his loyal agent Sammy (Eddie Marsan) in high-handed fashion and is contemptuous of the idea that he be asked to play an old “shipwreck of a man” in a wartime potboiler. It is typical of the film that someone who seems early on like a comic buffoon is given depth and pathos.

Their Finest often resembles the films it is so busy sending up. Early on, for example, the relationship between Catrin and her fellow screenwriter Buckley (Sam Claflin) is dealt with in such reticent and evasive fashion that it makes Ealing movies of the 1940s look melodramatic and expressive by comparison. The two writers are clearly attracted to one another but that doesn’t stop Buckley from lecturing and browbeating Catrin and continually telling her to be more economical with her dialogue. He’s offhand and cynical.

There is plenty of death and destruction in the film: horribly bloodied bodies that need to be identified in the morgue or victims of the Blitz lying in the rubble of what was once their homes. Amid all the carnage, no-one betrays any outward sense of grief. They simply get on with the job in hand in a typically British fashion.

If Nighy is the most shameless in his scene-stealing antics, several other character actors here are also trying to pilfer our attention. Richard E. Grant rolls his eyes and furrows his brow in fine comic fashion as the head of the film division at the Ministry of Information. Rachael Stirling plays her character (a caustic lesbian film executive from the Ministry of Information) with a Tallulah Bankhead-like world weariness.

Jeremy Irons appears briefly, reciting soliloquies from Shakespeare’s Henry V, and there’s an engaging cameo from Jake Lacy as a good-looking but dim-witted American pilot drafted in to star in the movie to please the US distributors. Some of the in-jokes begin to grate but the film has enough heart never simply to seem like a lampoon of wartime British cinema. Its recreation of Dunkirk using painted backdrops is ingenious. It will be intriguing to see how Christopher Nolan treats the same subject matter in his IMAX epic, due out later in the year.