The writers behind Liar explain why they revealed the truth midway through the series

The big reveal comes bang in the middle of a six-episode series. So – what now?

Liar is the work of The Missing screenwriters Jack and Harry Williams, who made the unusual choice to expose the truth to the audience halfway through.

"You expect to find out at the end, so therefore I think it felt a bit like, 'Ooh, what would happen if we pushed that earlier?'" said Harry at a press screening in London earlier this month.

"In The Missing, too, we revealed the killer halfway through and people were like, 'Why have you done that? What are you going to do next?'

"Well, won't that be interesting?"

Jack adds: "I think we've always approached our stories just as they evolve. The worst thing you can do is say: Let's wait until the end to reveal everything and then spend two hours of the audience's time going, 'Um - what are we going to do now?'"

But by exposing Andrew as the one who drugged Laura and removing that particular mystery for viewers at home, the Williams brothers are doing something very clever.

From the beginning it seemed unlikely they would have made Laura a false accuser. In a world where women are routinely disbelieved when they accuse men of rape, writing a TV drama where the rape "victim" was making it all up would have been pretty irresponsible. Dramatic – but harmful.

If Laura was telling the truth, the only way to exonerate Andrew would have been to introduce a "third party". Unfortunately, none of those theories were particularly plausible.

So instead of dragging out the mystery, the Williams brothers exposed Andrew's crime to the audience.

That also leaves space for Liar to explore new territory. We know that Andrew is a rapist, but the CPS won't prosecute the case – so it looks like Liar will reflect the reality that in the UK very few rape cases ever make it to court.

From the final few minutes, it seems Andrew may actually attack Laura in the legal system instead, pressing charges for defamation of character.

And DI Harman has warned the English teacher that he's a dangerous character who may have murdered his wife, so she should keep well away – but when has Laura ever done that?

At first glance it seems idiotic to blow the mystery of a thriller only halfway through a series, solving the central question: who's lying and who's telling the truth? But what if it does the opposite, allowing the drama to escalate beyond the framework we originally expected from it?

Speaking at the screening, Joanne Froggatt promised much more to come. "There's plenty more twists and turns after you find out," she said. In fact, "there's even more after you find out!"