Unfolding in near real time, this riveting thriller puts the ethics of drone warfare under forensic scrutiny by focusing on a diverse group of players (including Helen Mirren).

In four different locations, those at the centre of the action all have their own agendas and scruples as they strive to knock out a terrorist cell.

In Nairobi, Barkhad Abdi’s undercover field agent puts his life on the line spying on the terrorists’ safe house; from his base in Nevada, Aaron Paul’s conscience-stricken US air force officer agonises over his role as he pilots the Reaper drone flying overhead; Mirren’s steely colonel directs the operation from Surrey and remains unflinching when the mission’s parameters change; over in Whitehall, Alan Rickman’s sardonic army officer advises a group of politicians as they dither and try to pass the buck.

Screenwriter Guy Hibbert and director Gavin Hood rather over-egg the plot – adding a pair of would-be suicide bombers inside the house and a cute little girl selling bread outside – but even as they ratchet up the suspense it’s the characters’ moral dilemmas that prove most gripping.