Prime Suspect 1973 is by no means a bad show – but it has the misfortune to be airing alongside Broadchurch (and now Line of Duty on the other side) and really needs to up its game if it’s to compete.

With a suspect in custody for the murder case, episode five is almost entirely focussed on the impending bank robbery – cue a tense telephone conversation between bank robber Clifford Bentley and underworld leader Clay Whiteley, which ends with the latter telling the former that the robbery is to take place tonight or else…. Unfortunately we clearly see another night and day go by before it actually happens.

Maybe it’s a scripting error, perhaps it’s a mistake in the editing. Elsewhere, DC Hudson trails David Bentley to his lookout post on a (conveniently) deserted multi-storey car park. He trails him there on two different occasions, on two different days… As viewers of the modern age, of course we know that those two scenes will have been filmed at the same time – but the skill of the director is to fool us into believing otherwise. It needed a change of clothes, or lighting, or camera angle – anything to avoid the jarring confusion of momentarily thinking the narrative has jumped back a day.

There are other niggling details, small but rookie errors – the Superintendent’s right hand is behind his back in the reverse shot, but down by his side when filmed from the front. It’s hard not to think that the actor, the director, the editor, the producers, somebody should have picked that up. It’s certainly not something we can blame the script for.

That’s not to let the writing off scot free. Café owner Silas confesses to the police, but he doesn’t tell them anything they don’t already know; and later on his role is to alert the police when the robbery starts, but he doesn’t do that either. Why bother? It’s hard not to conclude it’s just padding, some scenes there for timing rather than story reasons.

Worse still is the contrivance required to give us what is, to be fair, a very dramatic ending. Being charitable I can just about suspend my disbelief over how long it takes the bank manager to get the vault open – but I’m afraid nothing could sell me on the idea that safe cracker John Bentley would lay his blow torch down, still lit (!) next to the gas tanks. There it remains for some time without anybody spotting it, so that just as the cops finally get through the door there is a huge explosion.

Full marks to the visual effects boys at least, who give us a spectacular fireball blowing the windows out, and rocking an innocent Triumph Dolomite on the road outside. No question, it’s a superbly dramatic cliffhanger to this penultimate episode, given that almost the entire cast is in the blast radius…. It’s just a shame that the preceding 55 minutes couldn’t quite match up to it.

Aired at 9pm on Tuesday 30 March 2017 on ITV.

Buy the complete original Prime Suspect series box set on Amazon here.

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