Even the producers of Unforgotten don't know the new killer

With the exception of the third series, which tipped its hand earlier in the run, a new suspect always emerge just when we have convinced ourselves whodunnit. Now even the producers are keen to avoid spoilers, requesting that Unforgotten writer Chris Lang keeps them out the loop.

Speaking at the BFI and Radio Times Television Festival, executive producer Laura Mackie explained, “we have made an interesting decision in series 4. In the past, [executive producer] Sally Haynes and I have always known who’s done it.

“This time we’ve decided with Chris that we don’t want to know. We’ve got five scripts now, Chris has written drafts of five out of the six scripts of series 4. We came in a few weeks ago and Sally and I were looking and ask each other who we thought could be the culprit and we literally didn’t know.”

However, Mackie insisted that this actually works as an advantage for them for when the series comes out.

“It’s actually great to be able to read it because then you are objective, you’re not bringing any baggage to it,” she continued. “But we do have notes, we do have little annoying anal notes that probably get on Chris’s nerves.”

The fourth series will see the return of police detectives Cassie Stuart (Nicola Walker) and Sunny Khan (Sanjeev Bhaskar) as they attempt to solve another case.

Lang added at the festival that it was their “ordinary” depictions as detectives on screen that made them “extraordinary” in televisual terms.

“Most TV detectives seem to often require external tropes in ordinary to make them seem more interesting,” he said. “They have a fast car or a drink or drug habit or a mental health issue or some kind of quirk that I think is a little bit bolted on because actually, watch 24 Hours In Police Custody and those guys have none of that crap going on, they’re just extraordinary because of the job they do and how they inhabit the word in which they live. I thought that was all you needed to show for it to be actually unusual.”

Unforgotten series 4 is set to return to ITV soon