VIDEO: Brighton-based TV detective series Grace smashes its own viewing figures

Episode one last year achieved 4.9 million. The consolidated seven-day viewing figure (on the night plus the next seven days on catch-up) rose to a remarkable 5.6 million.

Peter James – who wrote the series of novels the television series is based on – is thrilled: “I think it comes down to word of mouth. I think people are talking about it and that is great but also I do think the series has moved on. The actors have really now bedded into it and they have such a great rapport. I had lunch the other day with John Simm (who plays Detective Superintendent Roy Grace), and he was saying the fact is that he and Richie Campbell and Craig Parkinson and the others have become really, really good friends. He had worked very fleetingly with Craig Parkinson before but the fact is they've got such great chemistry.”

And that's absolutely something you cannot take for granted: “One of the most important things I learned in my years as a producer before writing full-time is that you can have the most amazing cast in the world but if they don't have that chemistry between them then you will end up with a total flop.” Peter cites a film he worked on, The Bridge of San Luis Rey starring Gabriel Byrne, Robert De Niro, Harvey Keitel and Kathy Bates: “And yet there was not one jot of chemistry between any of them and the film totally tanked. If there is nothing there then there is absolutely nothing you can do but when you watch Roy and Cleo in Grace, you can really feel that they are potentially lovers. Cleo came into it in episode three and she brings a great warmth to it. She was not physically exactly how I had imagined Cleo but she has absolutely got the warmth and the personality of the character as I imagined her. And I think the absolutely crucial thing is that Roy and all of them have really listened to Dave Gaylor, my real-life Roy Grace. It's hard to act as a cop and in all the times I've been out with the police, which is a huge number over 40 years, you really sense that they are a family. They have their own way of doing things and it is hard to replicate that. Also I was so passionate about researching everything and getting everything right because there are actually very few police shows that do get it right on television but this one absolutely does. They have really taken such care over it and I look at it and I think ‘Roy, I can really believe you as a policeman’ and I think ‘Glenn, I can really believe you as a policeman.” And that certainly feeds into Peter’s own viewing: “I'm finding that I'm just sitting there and enjoying it rather than wishing things had been done differently.”

This latest season has seen the emergence of the great enemy within, Cassian Pewe, and that has certainly added a new element: “He is just so horrible. I based him on a former senior policeman that I met. He was just so snide and so full of his own self-importance. I never met a single officer who had a single good word to say about him. He very nearly made chief constable but then got pipped for the job. There's no place for arrogance or conceit like that in the police. Police officers do a public service and the vast majority of police officers have gone into it because they want to do a job where they can make a great difference. When you get someone who is just there for self-aggrandisement like Cassian Pewe, then it becomes very dangerous.”

Meanwhile, amid the Grace success on TV, the success also continues on stage with the tour of Wish You Were Dead which plays Southampton’s Mayflower Theatre from June 6-10 and Worthing’s Connaught Theatre from July 10-15.