Unforgotten review: Serviceable if a bit naff

British television is brutal. The job security of actors, even in leading roles, is perilous. From the urtext, Spooks, where everyone from Keeley Hawes to Matthew Macfadyen cut their teeth, through to ITV’s returning Monday night drama, Unforgotten, writers have always been willing to throw their characters under the bus (sometimes literally). The challenge, then, is reacclimating audiences, once the dust settles, to a very different version of the same old show.

Back for its fifth season, Unforgotten is still reeling from the death of Nicola Walker’s Cassie Stuart. DI Sunny Khan (Sanjeev Bhaskar) is grieving, while incoming DCI Jessie James (Sinéad Keenan) is met by a rather cold shoulder. She doesn’t help herself: at home, her family life is falling apart, and the new gig couldn’t come at a worse time. Both she and Sunny are thinking of chucking it all in: Sunny is interrupted composing a letter (Chekhov’s “Resignation Draft.doc”?), while Jessie makes it to the chief superintendent’s door, before rethinking her decision. Is it possible that a gripping cold case will reel them both back in?

Helpfully, the mummified remains of a woman are found in the chimney stack of an abandoned house that is being fixed up for renovation. Rather than seeing this as an opportunity to break the ice with her team, Jessie tries to shut the investigation down. “I’m not sure why she even bothers turning up,” comes the judgment of DC Karen Willetts (Pippa Nixon). But, as ever with Unforgotten, the threads – from Paris to the Thames estuary – start to tangle into a pleasingly complex mystery, one that even Jessie can’t ignore.

Detective dramas are often more about work marriages than real marriages, and Unforgotten is no different. Jessie’s mum (Kate Robbins) remarks that her daughter was “always this person who could just cope with anything”. “But that’s hard for people,” she concludes, and even though she’s talking about the James’s disintegrating marriage, she could just as easily be referring to Jessie’s fractious dealings with DI Khan. Within the first couple of episodes, Sunny has declared that he doesn’t like Jessie, while the newcomer has branded the old hand a “d***”.

The brilliance of Walker, as an actor, is her ability to create an emotional brittleness beneath a tough veneer. For Keenan, it’s a hard act to follow. The centrality of the relationship between Sunny and Cassie has, inevitably, led to Keenan being referred to as a “recast” – an unhelpful, and incorrect, tag. “I am aware of the boots that I’m filling,” she tells the gang at Bishop Street police station, “and I sincerely hope to do her and all of her team justice.” These words could equally apply to Keenan, whose character’s slow thawing will gradually endear her to Walker’s diehard legion of fans.

Unforgotten has always been held up as quality TV. A thinking man’s Silent Witness, if you will. But, in reality, it’s still a bit naff. The casting brings together the top-end of British televisual actors – even if Walker’s gravitas is hard to replace – but remains somewhat parochial. There is no one here with the charisma or profile of Kate Winslet or Andrew Garfield or Idris Elba, all of whom have headlined detective dramas in recent years. But despite the rather limited scope of its ambitions, Unforgotten doesn’t fully commit to restraint. It might be mercifully absent of the shenanigans of Line of Duty or the raw implausibility of Luther, but the case is still grizzly, the class dynamics rendered in primary colours, the cinematography closer to EastEnders than True Detective. It is, in short, classic primetime ITV fare.

Even if this new season of Unforgotten is a touch underwhelming, Bhaskar and company remain a first-class ensemble, and the writing is thoughtful and well-paced. So long as you accept its limitations and are not in the market for something excessively cerebral, Unforgotten is a serviceable antidote to the relentless twists and turns, red herrings and double bluffs, of some of its competitors.