Channel 4's espionage drama The Undeclared War returns for a second season tonight, continuing Peter Kosminsky's cyber-thriller starring Simon Pegg as GCHQ director of operations Danny Patrick. The series explores the fraught world of intelligence and cybersecurity, and its return is notable for expanding both its plot and its cast, deepening the personal and political stakes established in the first run.

Season two picks up with Danny reeling from the shocking revelations of series one, both about government workings and his own marriage, as matters take a further turn for the worse. Colleague Saara (Hannah Khalique-Brown) uncovers irregular information flows suggesting a mole within the intelligence agency, driving a tense hunt through GCHQ. Adrian Lester returns as the prime minister, while Siân Brooke joins the cast as Danny's wife, a former MI6 officer, adding fresh intrigue to the drama. It airs at 9pm on Channel 4.