Below the Surface, Series Finale, BBC Four review - tense and twisty to the bitter end

In the previous couple of episodes, some light began to seep into the subterranean gloom of the Copenhagen kidnappers, or at any rate onto their identities and motivations.

The military theme with which Below the Surface opened, with Philip Norgaard (Johannes Lassen) being battered to a pulp by his captors somewhere in the Middle East, was proving to be the key to the mystery, as Norgaard himself suspected from early on. Now we knew that the terrorist leader was Mark Hald (Jakob Oftebro), previously believed killed in action, and that the hostage crisis somehow stemmed from the battlefield disaster which befell platoon K7.

In this final double dose (postponed from last week), the conclusion was played out in a skilful mix of action, tension, dirty realpolitik and intense personal anguish. TV journalist Naja Toft (Paprika Steen, pictured below), having enjoyed a little too much her headlining role as the high-profile connection to the hostages with her live blog interviews, had been left sorely chastened by being manipulated by the terrorists’ overground man “Ben” (in reality, the brother of another supposedly dead soldier). We also learned that she was also haunted by her failed attempt to achieve a journalistic coup by cracking a sex-slave ring, when her nerve failed her at the crucial moment (giving us back-story bulletins from individual characters has been one of the show’s trademarks, though sometimes an over-used one.)

Thus redemption was the order of the day as Naja volunteered to enter the lion’s den of the subway station, using the pretext of a final video interview to boost public donations to the free-the-hostages fund as a device to allow the security forces to breach the terrorists’ defences. This worked with almost supernatural smoothness, except for the last part, which left Hald threatening to annihilate the last trio of hostages unless Norgaard himself went down into the tunnel.

Once he was face to face with Hald, with a lump of Semtex explosive strapped to his chest to make sure he didn’t cheat, it finally became clear that resolution of the crisis depended on Norgaard unburdening himself of the weight of guilt and secrecy that had been crushing him ever since his return from his own captivity. That captivity, it transpired, had been shared for six months with Hald and another Danish soldier, Jim Hansen.

The story disseminated for public consumption was that Norgaard was the hero who made a daring lone escape, for which he had been rewarded with Denmark’s Medal of Bravery. The truth was more prosaic and significantly less flattering for both Norgaard and the Danish top brass, so it had been systematically covered up. “You’re a hero – learn to live with it,” Norgaard was ordered by defence chief Palle Wulff (Henrik Prip).

The hardest thing for Norgaard to swallow was that his vow to get his fellow-prisoners released had gone unfulfilled, but in his defence, he’d been blindsided with a pack of officially-sanctioned lies. Despite being the son of one of his country’s most eminent military men, he was still just cannon fodder in the greater game, while the subway hijack proved to be a last-ditch gambit by a desperate man (pictured above, Lassen with Henning Jensen as his father).

Below the Surface could be viewed as a meditation on the bonds that form between soldiers in combat and on the so-called military covenant, which defines a nation’s moral obligations to its armed forces. Or you could just call it a cunningly-designed thriller which didn’t allow its narrative grip to slacken (well, maybe it did a couple of times) and kept some surprises up its sleeve right to the bitter end.

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• Below the Surface is available on digital download from 8 April 2018 and on DVD from 9 April