The Spy Gone North is a sprawling epic, a tense, dense film that offers fresh insight into a newly relevant geopolitical conflict. Told over several years, it follows the highly secretive plot of a South Korean spy attempted to infiltrate the North Korean inner circle during the 90s. His mission is to expose the North's pursuit of nuclear weapons and the ensuing thriller feels unexpectedly pertinent.

Directed with confidence by Yoon Jong-bin, The Spy Gone North highlights why South Korean cinema continues to be an exciting, genre-stretching place. There are a lot of pieces to take in here, and while it initially feels like there is too much going on, the film rewards with a surprising amount of depth. It takes the time to add detail and grey areas to what on the surface feels like a standard battle of wits between competing sides. Particularly good are Hwang Jung-min and Lee Sung-min, whose performances steadily scratch away at our perceived notions about who is the hero and who is the villain.

The Spy Gone North is unafraid to jump into the politics of the Korean peninsula, with the film building towards a meeting with Kim Jong-Il. This sequence is the film at its tensest, with Jong-bin alleviating some of the tension with well-placed humour. Added to this is Jo Yeong-wook's nerve-shredding score (he was also the composer for Oldboy) and it is at this moment that film blossoms into something special.

That this is not the climax is probably a weakness for the film, as it continues, telling the true story as it is but losing something in the way of tension. Nevertheless, the film manages to find a hopeful note to end on, a surprise given the stakes and duplicity that is taking place. The Spy Gone North is a fine example of why South Korean cinema is always worth engaging with.

This is a London Film Festival preview and The Spy Gone North will be released at a later date.