NOT just a pretty face: Joan Smith (Sophie Cookson) with her boss, nuclear scientist Max Davis (Stephen Campbell Moore). Photograph courtesy uproxx

WHAT WOULD YOU do if you discovered that your elderly mum, in her hand-knitted cardigan with her arthritic fingers, has had a secret life that is of great concern to the authorities? A life that involved nuclear plans and spies, sex and political manipulation? You might try to laugh it off as a rotten joke, but if you’re an English barrister (Ben Miles) and the cops on her tail are not laughing at all, in fact they’re not even smiling, it’s a bit of a nightmare. The British spy film Red Joan, tells a riveting story which begins on these lines.

But based on the true story of Melita Norwood (1912-2005), Red Joan is a lot more than a sweet and sexy spy thriller. It’s about the complex undercurrent of Russia joining the Allied forces in the Second World War, and what this meant for the war but also what this meant for the notion of loyalties.

It’s also about a young couple on the cusp of war, standing on the turrets of Cambridge University and looking at the built-up world around them, wistfully imagining what they would have held on to and preserved, if they had had the power.

Joan Smith (Sophie Cookson) is a brilliant graduate in theoretical science. She’s also a woman in a world coloured by blatant sexism. And she’s pretty in an unadorned way. She falls in love with Leo Galich (Tom Hughes) a boy with Russian credentials and strong leftist leanings. And the bonds they tie around each other are complicated by her job, her professional loyalties and her beliefs in a peaceful future for the world, to say nothing of his needs.

With Judi Dench as the elderly Joan, the story shifts between eras, telling stories and reliving passions and intrigue. It’s a work beautifully invested in 1940s fashion and decor as it is one about the race to make a nuclear bomb, which the world faced. But by the same token, Dench’s role is honed to a deep level of empathy with an elderly woman with a past.

Told with impeccable clarity and a sophisticated sense of narrative pace, without sensationalist forays into the horror of war being fought as the story is told, this exceptionally fine film is ultimately about the victory of self-belief in a world riddled with aggressive understandings of ‘rights’ and ‘wrongs’, as ours is. When the press and police are at your door, there is no time for nuances. But as she does in the recent film Victoria and Abdul, Dench is put in a position to take mastery of the situation with a monologue at the end of the work which pulls the whole narrative to astounding nuanced cohesion and makes you remember the Norwoods of this world, who quietly shifted values on their axes.

• Red Joan is directed by Trevor Nunn and features a cast headed by Stephen Boxer, Stephen Campbell Moore, Sophie Cookson, Judi Dench, Kevin Fuller, Freddie Gaminara, Steven Hillman, Tom Hughes, Phill Langhorne, Simon Ludders, Ben Miles, Ciarán Owens, Robin Soans, Laurence Spellman and Tereza Srbova. It is written by Lindsay Shapero, produced by David Parfitt and features creative input by George Fenton (music), Zac Nicholson (cinematography), Kristina Hetherington (editing), Priscilla John and Orla Maxwell (casting), Cristina Casali (production design) and Charlotte Walter (costumes). Release date through Cinema Nouveau, Ster Kinekor: May 24 2019.