As Inspector George Gently calls again for an eighth series, stars of the show Martin Shaw and Lee Ingleby tell Keeley Bolger about punch-ups, dodgy hairdos and acting advice

A fan of retro fashion, Lee Ingleby has done well out of his role in Sixties crime drama Inspector George Gently. Now eight series in, the actor has managed to snaffle his character's Harrington jacket and one of his sharp suits. But there is one thing he just can't bear about working on the show. "God, that haircut," says the 39-year-old of the moptop he sports in the series. "It does my head in! I've had enough of that fringe," he adds, laughing.

With the fringe slicked back from his face, however, Ingleby can at least go undetected when he's out and about - unlike his co-star, Martin Shaw.

Instantly recognisable as the titular detective, Shaw is also still approached about the uncompromising Judge John Deed. Despite being cancelled eight years ago, the series still has "an enormous following". Shaw, though, has firm views on watching the repeats when they air. "I try not to watch, seeing as I don't get paid for them," he says. "Sorry, did I say that out loud?"

But with fresh episodes of Inspector George Gently starting this month, a six million-strong audience and presumably a payday looming for his work on the series, being spotted is just part and parcel of his job.

Crediting Inspector George Gently's success to the writing and the character-driven stories, both actors relished tackling some challenging subjects and scenes in the new series. Except for one maybe, which saw Shaw, also famed for his role in The Professionals, having to film an "incredibly difficult" set-to in the boxing ring, as his character lets off steam after a hard day's work.

"Professional boxers do it for 45 minutes; I was boxing for four-and-a-half hours, so it played hell with my shoulder," grumbles the 70-year-old, in his just detectable Brummy burr. "You lead with your left hand, but the stunt arranger asked me to do a few right hooks as well. The guy I was hitting used to be a professional boxer, and he was saying, 'Hit me, hit me, hit me', so I went, 'Fair enough' - bang! And I then felt this go," he recalls, lifting his hand.

Six months on and Shaw's hand "still hasn't recovered and is still swollen", he says, slowly waggling his fingers to prove his point. "That's dedication," notes Ingleby, who plays Gently's sidekick John Bacchus.

One episode sees Gently and Bacchus investigating a rape complaint. "It's not just about the 'whodunnit', it's about the characters and what was happening at the time," explains Shaw, who isn't a world away from Gently in his dapper shirt and braces.

The story throws up the differences between the two detectives' attitudes, with "old-fashioned" Bacchus not taking the woman's complaint seriously, and Gently having a more modern approach.

"Bacchus is going, 'You're wasting my time here, perhaps you were asking for it, you did lead him on', and not taking it seriously," explains Ingleby. "That's his ignorance coming through. Gently, of course, takes it seriously and opens Bacchus's eyes. Luckily, he does learn from it."

With a 30-year age gap between the actors, naturally, the father-son comparison crops up. "I'm the father," jokes Burnley-born Ingleby, who also starred in 2014 BBC drama Our Zoo. "We're mates," he adds - and Shaw agrees.

"The important thing is it's a very affectionate company," says the older actor. "Him and me, and Lisa McGrillis as well and Simon Hubbard, we're the four regulars. It transfers onto our guest artists as well. Both Lee and me have this ethos, which is you need to be kind, respectful and welcoming to everybody, because we've all had the experience of walking into a show where that's not the case - it's just hard to work, you know."

Having spent all his career on stage and screen, Shaw is even more convinced that good old-fashioned manners are vital for producing great performances. He recalls how he was recently asked to speak to some students at the prestigious performing arts school he went to, and give them some advice.

"The first piece of advice I gave them, was 'be kind'," he says. "It's nearly always very tense on set, everybody's tired and stressed, and if you can be as kind as possible, it really helps a lot." It's also helpful if you can "tell a lot of jokes - like him", he adds, gesturing towards his colleague. Though being of the "gobsmacking" nature, those jokes are not being shared today. "It just helps with the enjoyment," says Ingleby.

Despite the on-set friendliness and appeal of the storylines, the actors have differing views on whether they should start the cameras rolling on a ninth series. For Shaw it's a no, but his younger colleague would be happy for the series to continue.

"Get out the flares," says Ingleby, laughing. "It'd be interesting to see where it would go if it carried on into the Seventies. Bit of glam rock, I'd like to see that."

Inspector George Gently returns to BBC One, on Wednesday, April 29