One of the things that tempted Nettles, 48, back to the small screen after several years on stage was the fact that this new character, CI Tom Barnaby, was a 'tec without tics. "In the kit for Bergerac were his gammy leg, his drink problem and his divorce - it was a percentage game they were playing," he reckons. "I'd been 11 years as Bergerac, and I'd bored the English public with my leather jackets and red cars. He was such a dumb-dumb. The audience was always ahead of him."
"Mercifully, Barnaby has no such foibles," he continues. "I don't have to walk with a limp or have some extraordinary neurosis. I have to be quite ordinary - which is a special skill I've learnt. Barnaby is at ease with himself, and that makes a change."
Apart from the odd one-liner - he tells a colleague, "You're as politically correct as a Nuremberg rally" - Barnaby is as straight as a Roman road. His wife cooks him candlelit, Delia Smith suppers, and he leaves work early to be with his family - what would Morse have to say about that?
Pat Greenland, the associate producer on Midsomer Murders, takes up the theme. "Barnaby is a good detective with a solid family background, as opposed to a detective with a dysfunctional background like Morse."
The producer, Brian True-May, emphasises that "there are many quirky characters in the village in Midsomer Murders. Barnaby is the only sane person in the whole thing. He stands out as a mild man who knows what he wants. He's like Columbo with his `and another thing'."
All of which is true, but the burning question on every viewer's lips must be: why, oh why are we on patrol with yet another small-screen copper? Even Nettles at one point sighs that "the last thing we need is another television detective."
Greenland mounts a defence of detectives. "I've seen research that a university did on this and it said that detective drama is all about human relationships. Drama is essentially conflict, and detective drama is how people deal with that conflict," she asserts, before adding: "You can't ever have too many TV detectives."
Nettles, too, admits to a weakness for whodunits. "Whenever I go on on holiday," he confesses, "I always take Proust, but I always end up reading Agatha Christie. The conceit of the Home Counties mystery - that behind every chintz curtain lurks a murderer or that there might be mayhem between the silk sheets - is lovely." As Barnaby comments at one point in Midsomer Murders: "You wouldn't think that one small village would have so much trouble bubbling under the surface."
A chirpy, expansive presence, Nettles is talking to me during a break from shoot- ing. After successes over a five-year period at the RSC in such parts as Brutus and Leontes, he can talk with authority about acting. Anecdotes pour out thick and fast.
He was inspired to take up the craft by the example of the Angry Young Men in the early 1960s. "Tom Courtenay and Albert Finney opened doors for council-house boys like me to come into the profession. Suddenly you didn't need an upper-class accent and a pair of portable drawing-room windows to don the hose."
Despite the sometimes grave countenance he strikes on screen, Nettles has an appealing levity off it. He laughs that, "American actors are so serious. They explode with gravity. They need two pints of Windolene to lighten up. The bigger the star, the bigger the absurdity. Here I get treated with total contempt."
And he's all the better for it.
`Midsomer Murders: The Killings at Badger's Drift' is on tomorrow night at 8pm on ITV