Directed by Trevor Nunn. Starring Judi Dench, Sophie Cookson, Tom Hughes, Stephen Campbell Moore, Nina Susannah, Tereza Srbova. 109 mins. In cinemas now.

For a story about spying and espionage, Red Joan already feels like it’s gone through several disguises and undercover missions. This real-life story of Melita Norwood – a British civil servant whose pro-USSR espionage was revealed when she was an elderly retiree – was novelised by Jessica Rooney in 2014. Lindsay Shapiro then adapted it into a screenplay, here helmed by noted theatre director Trevor Nunn. It’s hard not to notice how the story has been watered down through its various iterations.

While the marketing pushes Red Joan as a Judi Dench vehicle, the beloved actress only appears briefly as the octogenarian widow Joan Stanley, suddenly accosted by police in her suburban London home. Charged with treason that has only come to light after the death of a former associate, she denies all charges, but flashbacks reveal her story to the audience.

Sophie Cookson plays a younger Joan, who was studying at Cambridge just before World War II. When she meets the handsome and charismatic Leo (Tom Hughes), a Jewish refugee involved in the Communist Party, she proves an easy recruit. Later, while working in an atomic research facility, the influence of an older professor, Max (Stephen Campbell Moore), and her own horror at Hiroshama and Nagasaki, inspire her to turn over British intelligence to the Soviets.

The story is potentially fascinating, as Joan isn’t portrayed as unequivocally pro-Communist, but pro-fairness. However, Shapiro’s clipped script and Nunn’s prosaic direction fail to provide any insight. Even Joan’s attraction to Leo and Max remains polite and passionless, undermining Joan further. It all makes for a decidedly underwhelming experience.