ITV and Mammoth Screen have begun filming on Betrayal, their new spy series set in the world of MI5. 

We first learned of Betrayal last year, with Shaun Evans (Endeavour) in the frame to star. Now, as filming begins, we have further names to round out the cast of this four-part ITV thriller.

Betrayal follows John Hughes (Shaun Evans), a mid-career MI5 officer grappling with a rapidly changing security landscape and his own personal demons.

When John’s clandestine encounter with a potential British-Iranian informant ends in bloodshed, he comes under scrutiny from superiors including Simone Grant (Nikki Amuka-Bird). As John navigates the murky world of espionage, the strain on his marriage to GP Claire (Romola Garai) becomes increasingly unsustainable.

Tensions escalate further with the arrival of Mehreen Askari-Evans (Zahra Ahmadi), a sharp, ambitious operative who has recently transferred from MI6, challenging both his professional standing and emotional control.

Also in the cast Gamba Cole, Omid Djalili, Matthew Tennyson, Hayley Tamaddon, Anthony Flanagan, Paddy Rowan, Waj Ali, Karim Kadjar, Emma Cunniffe, Georgina Rylance, Ben Lambert, Julia Watson and Julian Wadham.

Plus, television newcomers Elham Karimpour, Aidan Rivers, Corin Silva and Eliza Agrosoaie.

Betrayal comes from the award-winning playwright and screenwriter David Eldridge. It’s produced by Mammoth Screen and directed by Julian Jarrold (A Very Royal Scandal).

The series will air on ITV and ITVX in 2026. We’ll keep you posted.