Martin Shaw reveals why he had to say goodbye to Inspector George Gently

"It’s the right time," Shaw tells RadioTimes.com. "I mean, for a start, George is getting fed up with policing, you know, and the feelings that he has about his life, and just generally he is not suited to the modern police force."

The actor adds, "One of the show’s great assets is its realism and plausibility. And for George to carry on as an operational policeman, it wouldn’t have been realistic or plausible.

"It’s been a wonderful series. You know, it’s been a very, very happy ten years; it’s a great privilege to work on it, and I’ve loved it."

But while Shaw might be getting a little sentimental (understandable after ten years on the job), the 90-minute final episode avoids a sugary send-off.

The episode, titles Gently and the New Age, deals with some of the murkier aspects of politics. The nation has a new Tory Prime Minister, Ted Heath, but in the County Durham town of Washington the local Labour MP Michael Clements (Richard Harrington) has ambitious plans for a brand-new development – even if central government isn't keen.

Gently's final case turns out to be far bigger than even he could imagine as two murder investigations collide, with huge political ramifications.

"As we’ve seen, increasingly, the world of politics knows no bounds," Shaw says. "Whenever we think, 'No, however bad politics gets, it couldn’t be like that' – then you find out it can. Only this week we were being told that there were thousands of secret files about the Kennedy assassination about to be released, and who would have thought in our wildest nightmares that we were going to get a president in America like the one we’ve got now? Everything that we used to think was completely improbable is coming to pass.

"So there is absolutely nothing in this final episode of George Gently – where he’s upsetting the politicos – that couldn't have actually happened to a policeman who was determined to fight the system."

So how will the final episode end? "We’ve come full circle," Shaw teases.

When we first met Gently he had walked away from the Met in disgust because he knew about the depth of the corruption in the force. Now it seems he's on to something even bigger.

Inspector George Gently began with a pilot episode in 2007 and ran to eight series, popping up only semi-regularly on BBC1.

"When we did the pilot it was very clear that this had a very special quality," Shaw says. "I just loved doing the pilot, and I thought it was highly likely that it would carry on, but the great thing is we always had plenty of time off in between, so we never really found out whether it was going to be recommissioned until a couple of months beforehand.

"So each time it came up with another series it was, 'Oh, great, wonderful, here we go,' and we can catch up with all our mates again."