Inspector George Gently Books by Alan Hunter

Another set of books which inspired a TV series are Alan Hunter's Inspector George Gently series, starring Martin Shaw (of TV series The Professionals fame) as the main character.

A full list of titles (nearly 50 of them) can be found on Hunter's wikipedia page. As Hunter himself prefaces:

"This is a detective story, but NOT a whodunit. Its aim is to give a picture of a police investigator slowly building up his knowledge of a crime to a point, not where he knows who did it - both you and he know that at a fairly early stage - but to a point where he can bring a charge which will convince the jury."

From the 2007 BBC Press Release for the TV Series:

Britain, 1964: a time when the line between the police and criminals has become increasingly blurred; when the proliferation of drugs is about to change the face of policing forever; when Britain's youth stand on the brink of a social and sexual revolution. Inspector George Gently is one of the few good men at Scotland Yard, his sense of public duty an increasingly rare commodity in a police force where corruption is rife and unchecked. In Northumberland, George takes on the headstrong young Detective Sergeant Bacchus.

Writer and Executive Producer – Peter Flannery on adapting the series:

About four years ago I was rummaging in a dusty old bookshop when my hand fell on a paperback book called Gently Through The Mill by Alan Hunter.  Looking through it, I realised it was one of a substantial series of books featuring George Gently of Scotland Yard – the character and the writer being completely unknown to me. I bought the book for a couple of pounds and took it home.

This was not a completely random decision, nor was it inspired by any lifelong devotion to the detective fiction genre, which has always rather eluded me. But I had decided some while earlier to be on the lookout for a series of novels that could provide the basis for potential television adaptation.

To my surprise I found I enjoyed the novel, Gently seemed attractively old-fashioned, not just in his methods and his mindset, but in his values. I found there were dozens more in the series and that they were available for option. I started reading them avidly.

Martin Shaw on playing George Gently:

George is an old-time copper. He fought with General Montgomery in the Second World War; he's a very tough, seasoned fighter. He knows about hardship and has seen tough times, and that's a bonus.  I think he carries a lot of baggage around, what with the grief of the murder of his wife as well. He faces the seemingly impossible task of trying to change a corrupt police force – a one-man mission.