In a rather golden year for British television, one programme has stood a rather hunched head and shoulders over everything else in 2015.

For anyone wanting a reason to believe in life, love or BBC Four, then Detectorists is it. 

Not even Sharon Horgan and Rob Delaney’s fabulously filthy sitcom Catastrophe can quite match it.

Mackenzie Crook’s sitcom is pure sunshine in a bottle.  And as star Rachael Stirling states: “I have never met anybody who likes The Detectorists that I don’t like.

“If the sensibility of it appeals to something in somebody’s character then I’m going to like them because it’s so gentle and un-mean and un-malicious. It’s like a vital vitamin to some people.”

Rachael plays Mackenzie Crook’s partner Becky in Detectorists.  Rachael has her mum Diana Rigg’s cheekbones, a voice that sounds like nicotine and tobacco making out and a diary that is not so much full as fatigued.  “I’ve had an amazing year,” she admits. This autumn we’ve not only seen her in Detectorists but she’s been playing Toby Jones’ wife in the recent BBC One London drama Capital (confusingly, as Jones plays Crook’s best friend in Detectorists.  “I know. I’m a slut. I’m a tart,” she says when I point out as much to her.  “What can I tell you? Either that or casting directors don’t have much imagination.”

She also plays Winston Churchill’s daughter in an ITV drama, Churchill’s Secret, that will air in the new year. It also stars Matthew Macfadyen, Tara Fitzgerald and Michael Gambon as the “great” man.

There is also a Second World War film Their Greatest Hour and a Half in the offing, directed by Lone (An Education) Scherfig, in which she plays an “acid-tongued ginger lesbian”. Called Phyllis.  “No sex, please,” she points out.  “It’s rated for 12.”  She possibly needs to be clear on this because she has lesbian history.  She first came to prominence in the TV version of Sarah Waters’ novel Tipping the Velvet and that was nothing but sex. Really, though, she just wants to talk about Detectorists.  There is going to be a Christmas special, she says, but it’s only going to feature “Mac and Tobes”. No Becky then, which is a huge disappointment.

But Rachael, I say, I do have one worry about the programme – other than there won’t be a third series. Does it suggest that decent men, good men like Mackenzie Crook and Toby Jones, are just feckless? Does it present a picture of masculinity that is encouragingly anti-macho yet also essentially useless?

“Oh my god,” she (almost) shouts. “I think it does the opposite.”

Really? So tell me, who wears the trousers, you or Mackenzie? “Clearly Becky wears the trousers in that relationship.” And who changes the fuses? “Definitely Becky.” My point proved, I say.

But she’s not having it. “People have said, ‘Oh, we don’t quite believe in that couple.’ I believe in them. I believe in his wonderful peccadilloes and his curiosity.

“Mackenzie is quite like his character: his curiosity for things, his sense of humour. Mackenzie’s the yin to Becky’s yang.”

This seems a good point to talk about men and her attitude to them. She once said that she was attracted to an “old-fashioned masculinity”. Is that still the case, I wonder?

“I suppose I’m quite manly in lots of ways but I like to be made to feel like a woman.”

Manly? I hadn’t noticed. “I think I’ve got a lot of testosterone coursing through my veins.

“Who knows how to define masculine or feminine any more?

BUT when going out on a date I think there are certain old-fashioned manners that I still enjoy. I don’t mean that as an anti-feminist comment. I just mean it as a pro-women comment. There must be a place for us to exist and our differences to exist without one taking away from the other.”

These days she’s seeing Guy Garvey. That bloke who sings with the band Elbow. They met at a wedding. Has he written a song about her yet?

“Loads,” she laughs.  “ He puts his heart on his sleeve and it so happens to be half my heart now.  A lot of his solo album Courting the Squall is about us. We’ve had conversations about it.  “He’s never hidden anything from anybody ever. And I don’t really want every single piece of my life to be out there. So we’re just negotiating now.  “But he’s amazing. I’m just a northern bird through and through.”

Well, yes. She might live in London and have spent much of her childhood there but she sees herself as Scottish.

While her mum is acting royalty, her dad, Archie Stirling, is a landowner, a businessman and someone who has tinkered more than a little in theatreland. He’s also the laird of the Keir Estate.

“In my bones I feel like a Scot. I always have,” she says.  “My mum’s from Doncaster so whatever that is as a combination of Scotland and Yorkshire. It isn’t southern.”

Rachael spent her youth shuttling between London and her father’s home in Scotland.

“Where dad lives I know every hole in every field and everything on every tree and I swim in the river from April until October. And the view of Ben Ledi and Ben Vorlich from Stirling...” She can’t find the words to describe it.

“Every holiday I would get on an aeroplane or the sleeper train. We had some hilarious journeys on that with the gerbil in the Quality Street tin and the dog in the basket and the drunken guard.”

That continued after her parents divorced in 1990 while she was at boarding school.  She’s bored of talking about their divorce. It happened when she was 12. She’s 38 now. It’s not relevant.

Plus, the facts as reported – the newspapers led on the story that her dad had an affair with Joely Richardson – she says are an “absolute pile of rubbish”.  All that matters is that both of her parents are still very much part of her life and vice-versa.

What about boarding school, was it character building or a cruel and unusual punishment?  “Odd. Odd. Children are resilient. I really love the women who I met there and I really love who they’ve become.

“But it definitely develops a survival instinct in you early on which I don’t know what I’d do without now because it’s part of my equipment. But there was a great deal of bullying.”

You were bullied? “Oh yeah. I was really homesick when I first arrived. For two years I was sobbing and circling tears on my letters. I was not egregiously bullied and no bodily harm was inflicted but I was just a weak one in the pack because I was desperately homesick.”

But eventually she found her feet.

On the plus side, she says, the school had incredible facilities.  “One of them was this arts centre and in there was a theatre and a rehearsal space and an exhibition space and I remember when I was let loose on it in my second year.

“I started to put roots down and feel more confident. That was the turning point of boarding school in the frame.”

She hadn’t really been interested in acting before that.  “I’d been backstage in a theatre but I didn’t really know what Mum did. I knew what she was and I knew people would look at her funny. Dads especially.”

Yeah, well, let’s move on, Rachael.

She admits that when she got her first big job – a part in the film Still Crazy – she didn’t really know what she was doing.  It took her 12 takes to walk through a door and hit her mark.  “By the time I did Billy Connolly was clapping slow and sarcastically. Thanks, dude.”

She was still a student at Edinburgh University at the time. During filming she’d fly back up to Scotland for tutorials. Her mum, I’ve read, was against her acting.  “The thing is it does happen in other professions and I have tried my hardest not to be conceited about it. I’ve never waved it. I’ve got a different surname. I very much got my jobs off my own back.

“If I’ve had a sniff of nepotism I run off in the opposite direction. In the end you’ve got to serve the script. If you can’t do that you’re not going to get the job.”

If anything maybe there’s a reverse nepotism at play now anyway. After all her mum does turn up in Detectorists playing her mum.

Rachael is busy and happy and maybe, finally, comfortable in her own skin.  “I like my 30s and I’m really looking forward to my 40s. I think one of my many weaknesses is wanting to please people, wanting to be liked and I think it’s quite an infantile mentality.

“And as I get older I realise you can’t please everybody and it doesn’t matter. And that’s something I’m getting to now.”

Meanwhile, I’ve bought my sister the Detectorists box set for Christmas. But don’t tell her.

Detectorists Christmas Special is on BBC Four on December 23 at 10pm. Churchill’s Secret airs in the new year.