VIDEO: Roy Grace creator Peter James thrilled with latest ITV season for the Brighton-based detective

As Peter says, he always would have preferred for Grace never to be made at all than to have been made badly. He waited – and his reward is a Grace which exceeds all his expectations.

Series four, currently airing on ITV, has got You Are Dead to go out on September 15 and Love You Dead on September 22. And the great news for Roy Grace fans is that just as series four ends on TV so ends filming for series five in and around Brighton, ready for screening next year.

Peter said: “I am very consulted by ITV on the script and consulted on every cast decision even down to the smallest roles. And then I get what they call the weekly assemblies every Friday evening (during filming), the rough assemblies and then I get sent the full episode well in advance. But actually what my wife and I love to do is to actually watch the episode on the night.

“And every time I watch it I think ‘Am I dreaming?’ I waited for so long for Grace to happen but I didn't want it to happen unless it was made really well and I think ITV are making it brilliantly. I think the production values are fantastic but more than anything for me I think the big success is the wonderful cast. I do think from my old days as a producer that you can put the best actors possible together but if there isn't the chemistry there, it just won't work. If there is no chemistry, then you've had it but I'm so lucky that there is brilliant chemistry between John Simm and Richie Campbell (as Detective Superintendent Roy Grace and Glenn Branson). You feel that there is a palpable warmth. It is really like they are old mates. And the chemistry between John Simm and Zoë Tapper (as Cleo Morey, his wife) is fantastic too. You really do feel that they are in love.”

Peter recalls the day he met the copper who became Glenn Branson: “I had been going out in police cars from the mid-80s and in 1993 I was in a response car for a day and there was an older cop there, this huge tall black guy called Glenn Douglas, and I started talking to him. He told me that he had only just joined the police and that this was his second week out of probation and that before that he had been a nightclub bouncer. His first kid had been born and he said I looked at him and I thought ‘In a few years’ time you're going to be going to school and someone will ask you what does your dad do. And I thought ‘I want to do something that you are going to be proud of’ and so I joined the police.”

Douglas retired two years ago: “They asked me to do a video for his retirement party. He was a real gentleman giant, and so I sent a video saying ‘Thank you for being the inspiration for my Glenn Branson!’

One Of Us Is Dead, the landmark 20th novel in the Detective Superintendent Roy Grace series, hits the book shops on Sept 24.