The End User (2)

The finale opens with Clark and Naylor carrying the blame for an arms shipment that got through to Northern Ireland on their watch. It's a bad place to be, and it gets worse fast. Connell reveals she has been working for the police all along, and that she offered up her two former colleagues in exchange for a promotion. But the betrayal lands harder because it's Mo, the one who always held the moral line.

J. C. Wilsher and Dusty Hughes wrote both parts, Roy Battersby directed them, and the second half delivers the collapse. The pair end up trapped on a boat rigged to implode, and the episode strips everything back to the simplest question there is: will they make it out alive. The action is properly tense, but the real drama is the institutional one. Is MI5 in control, or has Deakin finally overstepped with his freelance operation? The answer the series gives is that it doesn't much matter, because the machine will absorb whichever version is convenient.

Siobhan Redmond's Connell is the performance of the finale, and the episode gives her the room to be awful and human at once. Tony Doyle's Deakin watches it all unfold with his usual calm, and the supporting cast, Robin McCallum's Graves, Richard McCabe's Skinner, the Special Branch officers played by Hamish McColl and Harry Gostelow, circle the wreckage.

It's a contained disaster ending with the rot exposed at last. The boat goes up, the trust is gone, and the series bows out on its favourite note: nobody gets out clean. The boat setting is a fine choice for a finale, a confined space where nobody can walk away from the reckoning. And the series' last question, who really holds the power, gets the answer it deserves: the people who don't have to explain themselves.