At first I thought this movie must have been inspired by "Oppenheimer", but then I noticed the year (2018), so it must rather be the other way around. The story begins with the police arresting a former female nuclear physicist who, before and during the war, handed secret documents about the British atomic bomb project to the Russians. She had been seduced by a KGB agent and was not a communist herself, but simply wanted everyone to have equal access to the terrible weapon. "Based on a true story," it said, and this I believed until I found out that the real spy, Melita Norwood, was neither a nuclear physicist nor a wayward romantic, but simply a die-hard communist who gave the Russians the recipe for the bomb in the hope of killing all enemies of the Soviet Union.

It's not the first time the movie industry has rewritten real-life events to fit into Hollywood schematics, and calling it a "true story" is close to false advertising. But in spite of most of it being pure fiction, the movie offers believable scenes from the early days of nuclear physics and classic melodrama with Sophie Cookson as the naive Joan who falls in love with a Jewish refugee that turns out to be a KGB agent. The older version of Joan being run through the police wringer is played by Judy Dench, who, as always, does a brilliant job.

Okay pastime and not much more.