Vigil episode 6 review: Fitting finale for the superb submarine drama

Meanwhile, after being unmasked as the Russian agent last week, Lorne MacFadyen's Doward found himself scrambling as he desperately tried to fulfil his mission, attempting to smother an already struggling Glover to death before engaging in another desperate attempt at sabotage. There wasn't, it has to be said, a great deal of nuance to MacFadyen's portrayal of an evil traitor – but from a pure entertainment point of view I thought he played it brilliantly.

Anyway, the real highlight sequence of the episode began shortly after Prentice had successfully pulled Silva from the torpedo tube, with the pair soon confronted by arch-villain Doward. Earlier in the series, writer and creator Tom Edge had talked about how the "mythical" nature of submarines gave the series the feel of an epic – and this was certainly the case here, as Prentice and Doward essentially jousted on the rapidly plummeting boat. Alas, Doward came out on top, with Prentice becoming the latest in a long line of casualties during the series. It's safe to say that by the time of his demise he had well and truly redeemed himself, after spending the early part of the series firmly in Silva's bad books.

Doward's work was still not done and he proceeded to chase Silva into the area of the boat that was in the process of being decontaminated. Here, the episode pretty much descended into full-on slasher territory – as the masked, knife-wielding Doward stalked a terrified Silva around the boat while bathed in bright red light. This section might not have been to everyone's tastes but it was absolutely superb – one of the most purely entertaining (and tense) sequences I've seen on the small screen all year. What a terrifically unique series this has been throughout its run, and this scene further underlined what an inspired decision it was to set a drama on a nuclear submarine.

Thankfully, with more than a little help from Tara Kierly, Doward was apprehended and arrested for his role in the conspiracy, while some stellar work from the Vigil crew stabilised the boat and an essential intervention from the Americans threw the Russians off the scent. The rest of the episode essentially served to provide closure to the various other plot strands, with some lovely moments along the way. I was particularly glad that Elliot Glover – one of the best characters on the series from the get-go – managed to pull through after I'd been all but convinced he was a write-off last week. There was a great moment as he regained consciousness while being treated by his former flame Tiffany Docherty, and she warmly told him, "you're going to be OK" while we also saw him reunited with his family at the episode's close.

And of course, we got the moment that all those flashbacks have been leading up to, as Silva returned to land and was reunited with Longacre, with the pair deciding to resume their previously broken relationship. I've been fairly critical of this particular plot strand throughout the series, and I have to confess that even at the series close I'm not all that convinced. Fans have certainly enjoyed it – with the portmanteau #SILVACRE regularly trending on Twitter – while others have rightly pointed to the relationship as a positive step forward in terms of representation in a prime-time BBC drama. I certainly can't begrudge anyone that, but the relationship wasn't so much weaved into the plot as shoe-horned in, with those regular flashbacks having been delivered in a rather clumsy fashion, in an otherwise wholly gripping script.

Those missteps aside this series has been a real triumph. Towards the end of the episode, we saw an intriguing tete-a-tete between MP Patrick Cruden and Rear Admiral Shaw, and it's clear that whatever resolutions might have been offered, the debate as to the need – or lack thereof – of nuclear weapons will rage on, especially as Cruden is aware of the Navy's lies regarding the cause of the trawler going down at the very start of the series. We ended the series just as we began, with one of Craig Burke's messages to Jade Antoniak. "I got up early today," he says. "It was still dark, but went down by the side of the loch, saw the sun come up over the sea, and birds out flying. And I thought about how beautiful this world is, how much I miss when I'm under the water. And then I thought of you." A little mawkish perhaps – but on the whole, Vigil has well and truly earned a bit of sentimentality.

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