But what is the series about and is it a true story? Here's all you need to know about The Walk-In.
When is The Walk-In on TV?
The five-episode drama airs weekly on ITV at 9pm, starting this Monday (3 October) and continuing on Mondays.
What is The Walk-In about? Is it a true story?
Viewers may well find many parts of the series plot familiar, as it is based on a true story of recent events.
Written by Jeff Pope (Philomena, Stan & Ollie) it follows the story of how a Neo-Nazi plot to kill an MP was brought down by an inside man.
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Matthew Collins is an activist and reformed Neo-Nazi who was forced to flee the UK in the 1990s after turning mole on the BNP, but has returned to Britain as a journalist for the anti-racist organisation, Hope not Hate.
He is dedicated to stopping the radicalisation of young white men into far right groups by using moles, or walk-ins, to bring them down from the inside, but has struggled to infiltrate one particular group offering a youthful image while peddling violent racism.
Collins did not manage to break into the group before things escalated towards the horrific murder of Jo Cox MP, and although the group became the first far right organisation to be banned by the government since the Second World War, he was convinced they had simply been driven underground.
Thinking that he has missed his chance to put an end to their activities, Collins is feeling hopeless - until one day, he is contacted by a young man claiming to be a member who wants to help him.
He says there is a new plot to murder a second MP and wants to work as a mole against them, plunging both himself, Collins and the group's targets into an extremely dangerous situation.
Who stars in The Walk-In?
Stephen Graham, known for his work in This Is England, Line Of Duty, Time, The Virtues and Help, plays the lead role of Collins.
West End star Jodie Prenger also appears in the cast as DC Buckley.
Other actors in the series include Jason Flemyng (Lock, Stock and Two Smoking Barrels, Snatch), Dean-Charles Chapman (1917, Game Of Thrones), Leanne Best (Four Lives), Andrew Ellis (This Is England) and Christopher Coghill (EastEnders).
The Walk-In begins on Monday on ITV at 9pm.
Watch: See the trailer for true-life drama The Walk-In, starring Stephen Graham