The Undeclared War takes place in the post-pandemic world of 2024 against the backdrop of an upcoming British general election involving the UK's first Black Conservative prime minister. It tracks a leading team of analysts at the heart of the UK's NSA-style spy agency GCHQ as they attempt to ward off a cyber-attack on the country's electoral system.

Pegg features as Danny Patrick, GCHQ's head of operations, while Rylance plays John Yeabsley, a GCHQ old hand, who is brought back into the fold to support former colleagues in combatting the heightened threat level. Saara Parvan is a young student doing work experience in the GCHQ Malware Department, while other characters include Kathy Freeman, an American cyber-analyst on attachment at GCHQ from the NSA, and GCHQ head David Neal.

The Undeclared War Series Guide

• View Season 1 Episodes