One of the surprises about actors is how unlike their public selves they often are in real life. Stars who sparkle and charm in chatshow studios and red-carpet interviews can be startlingly flat when the TV cameras aren’t around. As Diane Morgan’s public persona is already Eeyoreish – dry, laconic, deadpan – were she to turn out in person to be much lower key, I wasn’t sure how we would get through an hour together.

She is posing for photos when I arrive, but breaks off with a megawatt beam, as if an old friend has just walked in. Her eyes somehow seem to occupy about 50% of the surface area of her face, and when she smiles her mouth takes up most of the other half. The effect is a dazzling blitz of warmth, the kind that can’t be faked and is found only in people who are unusually at ease with themselves.

Morgan can’t think why so many actors regard interviews as a disagreeable duty to be endured. “God, no, it’s fun,” she says. “I love talking about myself! Why would you not want to talk about yourself?” Like her heroine Victoria Wood, she likes to switch between self-belief and deprecation, one moment the caustic northerner with a keen ear but little time for pretension, the next a gauche ingenue baffled by anywhere more cosmopolitan than Bolton. The perspective she chooses appears to depend entirely on which is likely to be funniest.

There are no rehearsed jokes or well-trodden monologues. Morgan’s humour is located instead in dialogue, making her an unusually good listener. Primed to find comic possibilities in even the most innocuous exchange, she is so generous with her laughter that I leave under the happy delusion that I’m much wittier than I actually am. It’s only when I listen back to the tape afterwards that I realise Morgan was just funny enough for the both of us.

Fans of her Philomena Cunk character on Charlie Brooker’s Weekly Wipe of course know all this already. As the bafflingly dense yet unexpectedly perceptive Cunk, Morgan brings an absurdist eye to current affairs, and interviews unsuspecting experts in the idiot-savant style of Ali G. The political economist Will Hutton looked as though he might never recover from her furrow-browed inquiry, “Where is the money in a coin?” She has appeared in Peter Kay’s Phoenix Nights and Craig Cash’s Sky sitcom Rovers, and was for years a successful standup. But at 41 she is about to reach a far wider audience, as one of the stars in a new BBC comedy, Motherland, created by Sharon Horgan, Graham and Helen Linehan, and Holly Walsh, about the hell that is the primary school gate.

Morgan plays Liz, a slatternly, single, chaotic anti-heroine with a decidedly relaxed parenting style. In last year’s pilot we saw her very nearly cut her finger off after hacking away at frozen cheese (Liz stores all food items in her freezer, including eggs), pick a drunken fight with the flawless alpha mums who accuse her of sleeping with one of their husbands, and display no discernible attachment whatsoever to her children. The new six-part series will, she grins, “Be sort of more of the same, really. It’s about kids ruining people’s lives. That’s basically the gist of it. More kids, ruining more people’s lives in different ways.”

I've never done a sex scene and never will. Unless it's funny. But a serious sex scene, it would give me the creeps

I tell her I found the pilot horrifyingly recognisable. “Do you know what? I think a lot of mums did,” she says. “They will run up to you in the street and go, ‘Oh, thank God someone’s made a programme about this, because I thought I was the only one.’” Morgan chuckles dryly. “You can see the desperation in their eyes.”

It’s a surprise to learn that she and Horgan hadn’t previously known each other, for the part feels as if it was written specifically for Morgan. “No, but I’d admired her from afar, because she’s amazing. She’s lovely and gorgeous and funny – and she’s beautiful as well.” She curls her lip jokingly. “That’s the annoying thing.”

Morgan was on holiday with her boyfriend in Dubai when her agent asked her to audition. “I had just finished filming Cunk On Christmas, and I was absolutely chilled to the marrow and I said, ‘Where can we go on holiday that is guaranteed hot? I don’t need views. I just need a beach and hot.’ And then my agent says, ‘This script is from Sharon Horgan,’ and I read it and thought, ‘Oh my God, this is actually funny.’ It’s really rare to find a script that makes you laugh out loud, and this did.”

She ordered a breadknife from room service and filmed the cutting-off-her-finger scene on her iPhone in the hotel room, with her boyfriend reading the other mum’s part. “Then we went back to the pool and I’m thinking: I won’t get it. But apparently Graham Linehan said, ‘As soon as we saw the video, we knew we’d found our Liz.’” She laughs. “Too right you found your Liz, mate.”

Morgan with co-stars Paul Ready and Anna Maxwell-Martin in competitive parenting comedy Motherland. Photograph: Colin Hutton/BBC/Delightful Industries/Merman

The new series will feature a children’s party complete with entertainer – a rich comic seam, as any parent can confirm. Liz’s ex makes an appearance, which does not go well. And does she get accused of sleeping with any more husbands? Her smile glimmers with knowing mischief. “I do try and get off with someone, and that goes badly wrong. I did have to do a sort of kissing scene, which I’m always embarrassed about.”

She never feels self-conscious about the person she’s kissing – “Oh no, I’m not bothered about him” – nor does she mind strangers like me watching. “No, it’s not you; it’s about my mum and dad seeing it. They go, ‘Oh my God, look at Diane, argh.’” I ask if she has ever done a sex scene and she stares, mock-appalled. “No, I’ve never done a sex scene and never will. No, it’s not for me, no thanks. Forget it.” She pauses to think. “Unless it’s a funny sex scene. But a serious sex scene, I’d feel embarrassed. I’m just not that good an actor. No, it would give me the creeps.”

Motherland’s queen alpha mum is Amanda, played by Lucy Punch. “Hilariously chilling,” Morgan grimaces. “And we’ve all known one… we’ve all known an Amanda. I wonder if they recognise themselves if they’re watching it. I bet they wouldn’t.” Morgan doesn’t have children: “But you come across the Amandas even if you’re not a mum.” She shudders. “They move among us.”

Morgan is such a mixture of confidence and vulnerability, I can’t guess whether she finds the Amandas of this world intimidating or risible. She considers the question. “I think they get to me less and less, the older I get.” And the more successful she gets? “Yes! Absolutely.” She looks relieved that I’ve said it so she didn’t have to. “Yes, you can go, ‘Oh, I don’t care’, because,” and she gestures around us at the photographer’s studio and the Dictaphone on the table, “I’ve got this.”

***

Morgan didn’t always have “this”. The daughter of a physiotherapist and a full-time mother, she grew up with her brother, now a joiner, in Bolton, “and I suppose, looking back, it was a working-class upbringing. I still think of myself as working class, even though technically I’m probably not.” It was a happy childhood. “But we’re not that close-knit, really. I mean, I only sort of introduced hugging into the family a few years ago. Before, it was like” – she adopts a gruff, stiff tone – “Right, bye then.” How did the hugging go down? “It was, ‘Oh God, Diane’s been to drama school and now she’s hugging us when she leaves’, you know?”

I loved comedy, and I’d tape it off the TV and repeat it. I was such a lunatic. You’ve got to be a maniac about it

On Saturday nights the family would always gather around the television, “watching comedy, comedy, all comedy. Obsessed with comedy, all of us.” Did they compete to make each other laugh? “Yes, yes, but probably me more than others, because I got such a good response. I loved it, and I loved comedy, and I’d tape it off the television and repeat it. I was such a lunatic. I think you need to be like that. You’ve got to be a maniac about it.”

It’s hard to imagine the young Morgan as a precocious stage school type. “Yes,” she agrees. “I remember telling the school careers adviser that I’d like to be an actor, and she looked at me like I’d said, ‘I’d like to be a mermaid, please.’ So I didn’t tell that many people, and I thought, ‘Well, I’ll go to art school, because I can paint and I enjoy drawing, then I’ll try and see if I can get in through the back door to acting later on.’”

At her art school interview, the admissions tutor remarked that her portfolio was excellent, but she didn’t seem very enthusiastic and was there something else she’d rather do? “It must have been seeping out of my pores. Stupidly, I said, ‘Well, actually, I’d like to be an actor.’ At an interview for an art school! What a berk.” The interviewer closed her portfolio, slid it across the desk, and told her, “Well, go and do it.” Morgan’s eyes shine. “That was the first person who said, ‘Go and do it.’ And I thought, ‘Oh my God, yes. I’m going to go and do it.’”

She spent the next few years failing to get into drama school. Meanwhile, she did “lots of horrific, hideous jobs”, selling makeup for Avon, packing worming tablets in a factory and peeling spuds in a fish and chip shop. “Called Le Chipperie. True story.” Another aspiring young Bolton actor, Maxine Peake, was unsuccessfully auditioning everywhere at the same time, and the pair became close friends, even taking elocution lessons together, “thinking it must be the northern accent they don’t like”. When Peake won a scholarship to Rada, followed by a part in Victoria Wood’s Dinnerladies, “I was so upset and jealous! It was all I’d ever wanted, and she’d gone and done it. And she knew it, she knew it. We used to sit on her bed and read Victoria Wood books together and read out her sketches.” Morgan shakes her head and laughs. “But it all worked out in the end. Good job, too. I mean, if I hadn’t had any success, I probably would have hunted her down and shot her.”

At 20, Morgan won a place at East 15 drama school in east London, but failed to find work after graduating and spent the next five years doing telesales. “People were quite rude, so I would say things back to them, and people in the office would laugh. I’d slam the phone down and my boss would go, ‘Diane, you should do standup.’” She thought he was mad. “Not in a million fucking years. I couldn’t think of anything more terrifying.” After a couple more years of telesales, however, “I thought, ‘What the hell am I doing with my life? This is awful. Do you know what? I might give standup a go. What’s the worst that can happen?’”

To Morgan’s astonishment, very soon she was earning a living as a comedian. Inevitably, she had to contend with the “women can’t be funny” prejudice. “You can feel that the minute you come on.” She pulls a dejected expression: “‘Oh, it’s a woman.’ And sometimes I’d do a gig and a man would come up afterwards and go, ‘I’ve never found a woman funny before.’ Or, ‘I didn’t think you women could be funny, but you made me laugh.’ But I suppose that drove me on and made me want to do it more.”

The buzz was “like nothing else. You feel incredible.” But it was lonely work, and after nearly 10 years on the road, “Eventually I felt nothing. If it went well, I felt nothing. If I died, I felt nothing. I thought, ‘I can’t do this any more.’”

‘Getting that part changed everything’: Morgan as Philomena Cunk in mockumentary Cunk On Shakespeare. Photograph: BBC/House of Tomorrow

The ennui was well timed, for just then her agent sent her a script for Wipe. “I was so excited, because I’ve always been such a massive Charlie Brooker fan. I was like an X Factor contestant. I was like” – and she mimics a desperate wannabe – “‘I need this. I need this more than anyone!’”

Philomena Cunk had originally been conceived as a posh Tim Nice-But-Dim character, but when Morgan rehearsed she found it funnier in her own voice. At the audition she dutifully played a vacuous Sloane, then took a deep breath and asked permission to replay it with Lancastrian vowels. She thought they looked unimpressed, and afterwards, “I had to have a bit of a shop. I buy something because I’m like, ‘Oh, I’ve just made a fool of myself, oh my God, I’ll probably never hear about that ever again.’” When the call came to say the part was hers, “I screamed. I think I even cried. I’ve never wanted a job more in my life – and it changed everything.”

Her dream Cunk interviewees would be Prince Philip or Boris Johnson, but her character is becoming a casualty of its own success, too well known to dupe unsuspecting subjects. Morgan herself, however, is thoroughly enjoying her fame, and currently occupies that happy stratum of celebrity in which her fans are people she would like. “They’re always lovely. And I’m so grateful, because they’re the ones that have allowed me to do this. That sounds so wanky, doesn’t it? But it’s true, isn’t it? So it’s a lovely level of fame, really. Only nice, intelligent people come up to you.”

She is currently writing a comedy for Peake and herself, but has no ambitions to diversify into straight drama. “I’m generally not interested in Shakespeare or Broadchurch. I only want to make people laugh, really. I don’t want to play a copper. I couldn’t do it. I want to play oddballs. I want to play weirdos. There’s not enough weird. Everything just seems a bit mainstream to me, and I long for anything that’s a bit unusual.”

I never wanted children. Couldn’t see any advantage to having them. I just can’t, and I’ve always felt the same way

She barely even watches television nowadays. She likes Curb Your Enthusiasm, Adam Curtis documentaries and Tales Of The Unexpected. “And I watch weird documentaries from the 1970s about the paranormal. But apart from that, I don’t really. And once I’ve seen something, I think, well, I’ve seen that now. I don’t feel the need to get a box set out and watch 47 episodes, because I can feel my life ebbing away.”

She doesn’t go out much, either. “Oh no, I’d rather stay in. I’m not a big drinker, you see, so you won’t find me down the pub very often. I might go to a screening or something, but I won’t be there at two o’clock in the morning.” She used to live in Dalston, the hipster heart of London, but when I ask if she got involved in the social scene, she looks incredulous. “No, of course I didn’t. I only lived there because someone had a room, that was it. I’ll live anywhere. I’m from Bolton, you know. Everywhere seems nice.”

She now lives in Bloomsbury, having moved in with her boyfriend Ben Caudell, a BBC comedy producer. “I know, what a jammy sod,” she chuckles. “He lives in Bloomsbury, so I’ve fallen on my feet. It’s very near a bin yard where he lives, mind. Perilously near a bin yard. Not vineyard – a bin yard. But still, I do swan around a bit. I’ve been known to swan around. Why not? Could be dead next week.”

Today she looks like a rather fabulous Bloomsbury set beauty in her vintage Frank Usher dress, with her glossy chestnut mane, but says she’s never normally this glamorous. She dyed her hair herself – “Out of a box, mate” – and is starting to regret her pale pink gel nails. “Bit suffocating, to be honest,” she admits, eyeing them doubtfully. “Plus, they look really thick. I said, ‘Don’t put another coat on – that’s enough, mate.’ But I think I’m enjoying them. It’s a bit of fun, isn’t it?”

‘We live near a bin yard, not a vineyard’: with her boyfriend Ben Caudell, a BBC comedy producer. Photograph: Can Nguyen/REX/Shutterstock

I’d assumed that by now she must be wealthy, but she exclaims, “Oh God, no, I’ve got no money. I’ve never had money. But I’m not that bothered about money. I don’t want a swimming pool. I’m happy as I am. I don’t need much to be happy, and I’ve got what I want. I just want to do some good work now. I just want to do work that I’m not ashamed of.” She laughs. “That’s all I want.”

One thing she definitely does not want is children. The irony of landing a breakthrough role on a show about mums is not lost on Morgan, but she could not be clearer. “No, I never wanted them. Couldn’t see any advantage to having them. I just can’t, and I’ve always felt the same way. When I was younger, I thought, maybe I’ll change when I get older, but I haven’t.” She starts to chuckle. “Occasionally, people come up to me with kids and they’ll say, ‘Seriously, don’t have them. They ruin your life.’ But even if they didn’t say that, I’ve made my mind up now, and I’m with someone who doesn’t want kids as well, which is glorious. It’s really good luck.”

When I own up to having children, she offers the sort of sympathetic glance one might give to someone with an obscure medical condition you’ve never heard of that doesn’t sound very nice. “Hmm. I never fancied it. Aside from all the pain, they just sponge off you for the rest of your life then, don’t they? But then,” she muses, suddenly deadpan, “you’ll have someone to look after you when you’re old. Whereas I’ll be eaten by my own dogs, won’t I?”

• Motherland starts on 7 November on BBC2 and on BBC iPlayer.

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