While Primeval has rarely been the most adventurous of shows (curious, given its premise), it does at least attempt to liven things up by often presenting our team of dino-hunters with an anomaly in new and exciting locations. As such, we’ve seen episodes set in shopping centres, local schools and even at weddings. Usually, however, the settings are simply excuses for a basic change of scenery, and don’t add much to the story or change the established Primeval formula much.

However, this episode, which finds the team posted to a state-of-the-art submarine to investigate an underwater anomaly, provides far more thrills than the series usually allows. After the sub encounters the anomaly, the crew finds themselves with a small – but vicious – creature on board, and so the team return with them into the ocean to try and return it through the portal, inadvertently ending up sucked through into the ocean of the Cretaceous period. Little do they realise that the creature inside the submarine is nothing compared to what else lurks outside in the deep…

The submarine setting is an eccentric staple of genre shows and is used to fantastic effect here. The location is claustrophobic enough on its own, but the added element of a loose dinosaur running around the narrow corridors leads to a heavy and uneasy atmosphere, giving us a situation where we actually feel the fear of the characters. Too often the show is laminated, lacking any real sense of peril, but not here.

Meanwhile, back at the ARC, Lester finds his authority challenged in classic “Who’s in charge here? Not any more you’re not!” fashion, as the head of the Navy asserts control over the operation, taking it upon himself to launch another submarine with the intent of blasting the anomaly shut – with a nuclear warhead, no less!

Aside from the main submarine plot, there are also some references to previous episodes and storylines, which come as a refreshing reminder that Primeval doesn’t have to consist purely of standalone stories. Acknowledgement of previous events, such as Matt’s non-romance with Emily, and Abby and Connor’s year lost in the Cretaceous, help make the show’s world and its characters feel all the more real.

There’s also a hilarious meta-moment, which may or not have been intentional, where Connor has a go at Matt for stating the obvious, which plays as a subtle dig at the quality of the show’s dialogue. Similarly, the calibre of the supporting characters in most episodes is often of a pretty low standard. It’s very rare that we come to care about any of the guest-stars before they inevitably get eaten by monsters, and unfortunately, even in a better-than-average episode like this, the peripheral characters – in this instance, the skeleton crew of the submarine – feel underwritten and eminently disposable.

But, those almost default Primeval criticisms aside, this episode is far more exciting and accomplished than we’ve come to expect from this show of late. There’s a genuine sense of danger, and the submarine setting is more than just an excuse for a different set, with the location truly being used to its full potential. It has its fair share of implausibilities; the notion that Abby and Connor would be able to pilot a state-of-the-art submarine is laughable, while the fact that the Navy head’s threats to detonate a nuclear warhead off the coast of Britain in the Cretaceous period are met with barely a raised eyebrow by Jess and Lester is ridiculous, given the potentially time-altering repercussions.

On the whole though, this is the most fully realised episode of Primeval in quite some time, reminding us that the show can be rather exciting and scary when it puts its mind to it. Here’s hoping the remainder of the Series 5 can keep up the momentum.

Aired at 8pm on Tuesday 31st May 2011 on Watch and at 5.40pm on Saturday 23rd June 2012 on ITV1.

> Buy the Series 5 DVD on Amazon.

What did you think of the episode? Let us know below…