Viewing figures for repeats of the BBC One show regularly leave prime-time programmes trailing in the dust and New Tricks star Amanda Redman thinks she knows why.
Glamorous in a pale silk top with her blonde hair in a neat bob, set off by a deep tan, Redman, who turns 50 in August, explains: "We get really positive feedback from real officers, saying that out of all the police dramas on television, we're the most true to what they know happens in real life.
"They say the banter and the humour is absolutely correct as well as the police procedure - we're really strict on that."
She's right about the quality of the banter. The chemistry between the four main characters - DS Sandra Pullman (Redman) and retired police officers Jack Halford (James Bolam), Gerry Standing (Dennis Waterman) and Brian Lane (Alun Armstrong) keeps viewers entertained.
All the actors are sitting with Redman as she talks about the show, and hardly a minute passes without one of them cracking a joke, making the others fall about laughing.
"It's weirdly happy, it is honestly!" she says. "You even get crew members coming in saying, 'We love this, it's Monday again and we're at work'. How weird is that? It just doesn't happen normally, we must sound like the Waltons!"
New Tricks is back for a sixth series with what the cast describe as some of the most gritty cases yet, touching on racism, wife beating, UFOs and Brian's alcoholism.
"The viewers are more comfortable and familiar with New Tricks now, so that allows you to go into a darker place without them feeling threatened," says Redman.
At the end of series five, Brian was back on the bottle and his colleagues now have to deal with the effects of his alcoholism.
"This series looks at the truth of how people cope with somebody, either colleagues or family, who drinks too much - and it's very lonely. There are some very heavy emotional episodes in this series."
All the characters have a few skeletons lurking in their closets, none more so than Jack, who Amanda describes as the "darkest of all".
As for DS Pullman, she's torn between following strict police procedure and the boys' rule-bending tendencies.
An ambitious officer, she was sidelined into UCOS, the Unsolved Crime and Open Case Squad, after an incident in her former high-flying Scotland Yard career.
"The strength of New Tricks is that sometimes we can do some quite light stuff, so the whole tone of the episode is quite light, but the next episode we can go really quite dark," says Redman.
"It's one of those rare series where you can go anywhere, there is no ceiling on it."
And for that reason, we may well see a seventh series next year. "The BBC wants to do another one," she admits, "but there's no point doing it just for the sake of it. As long as we feel we've got something to give... but you just don't know."
The four stars certainly want to reunite - if for nothing more than the happy feeling on set.
"You're never going to believe it, but we never fall out. It's odd," says Redman. "It's not ego-driven for a start, so you don't have any of that rubbish going on, we're not like, 'My close-up'. We say, 'I don't want one, but he might'," she adds, pointing at Waterman. "And then he'll go 'sod off!'.
"If one of us feels particularly strongly about something, then the other three will back them up."
Of course she's aware that there is an obvious gender imbalance in the show and she accepts that it would never happen the other way around.
"I'm not saying that older women can't hold a show like this - three older ladies and a younger man sounds marvellous, but it wouldn't happen."
Despite the implicit sexism of her industry, Redman clearly loves her role as the only serving officer in a team investigating cold cases and she enthuses about "my boys".
Another strength of the show is the calibre of the guest stars it attracts. The new has appearances from Richard Wilson as a monk and Fay Ripley as a sex therapist, as well as Imogen Stubbs, Hugh Dennis and Diana Quick. Waterman's daughter Hannah also returns as his on-screen daughter.
"I think the truth is that these people actually phone up and say 'we'd like to do New Tricks', which is fabulous," says Redman.
Born in Brighton, she learnt her craft at the Bristol Old Vic Theatre School, before making her name in TV shows throughout the Eighties and Nineties, including El C.I.D and Dangerfield.
She married actor Robert Glenister - brother of Ashes To Ashes' Phil - in 1984, and has a daughter Emily, who is also an actress.
The couple divorced in 1992 and Redman now lives in West London with her long-term partner Damien Schnabel.
New Tricks shoots for six months of the year, leaving the cast free to work on other projects. But for the first time this year, Redman's having a break.
"I am going to take these six months off, but that's only because I was doing Little Dorrit last year and then straight into this and then I'm directing a show for my drama school (in Ealing).
"Normally I wouldn't take any time off, but I'm just a bit tired at the moment," she says, looking slightly downcast.
It's a rare admission from the bubbly actress and no sooner have the words popped out than Waterman makes a joke and she's smiling again.
Extra time - Amanda Redman
Amanda teaches drama for children and adults at Ealing Studios on Saturdays.
She reportedly had a relationship with her New Tricks co-star Dennis Waterman in the Eighties.
The skin on her arms is badly scarred from an accident involving a pan of boiling soup when she was just 18 months old.
She starred in 2000's Sexy Beast alongside Sir Ben Kingsley and won a Bafta nomination for her role in TV series At Home With The Braithwaites.
Amanda loves theatre and period drama and says there are "tons" more roles she would love to play.