The cast of Broadchurch, starring David Tennant, didn’t know the culprit until the last moments of filming.

Writer Chris Chibnall was so determined to keep the climax a surprise that he kept his cast and crew in the dark for the whole of the five-month filming schedule.

They had the kind of security you’d expect from a Hollywood blockbuster, Chibnall said. ‘All of the scripts on set were kept  in a safe, watermarked so they couldn’t be copied, and only five people knew the full story.

‘David Tennant grabbed hold of me and said he couldn’t believe I wasn’t going to tell him. But then he admitted he was actually glad.’

The actors were told on a ‘need-to-know’ basis a couple of days later in late-night phone calls just hours before they were due on set.

 Just adds to the mystery if you ask us… to read our own suspicions, click here