Ice queen: Sophie Ellis-Bextor, pop's coolest diva

After taking three years off to make an album and a baby, Sophie Ellis-Bextor had a big comeback gig - last New Year's Eve on BBC1. The midnight slot, no less. There she was, poised and ready to sing her new single, knees jiggling, gold Paule Ka dress glimmering. The rhythm started, the bass kicked in. Her lips moved, but nothing came out. It was a microphone malfunction to make Job weep. (The footage is now enshrined for universal Schadenfreude on YouTube.) As she blew bubbles, BBC1 tactfully cut to images of fireworks in Cardiff and people letting off balloons in Blackpool.

"That was actually the worst thing that ever happened to me," she says. But being Sophie Ellis-Bextor, the pop diva made of ice, she says it in the same tone as she would order a library book. You know that flat, expressionless thing she does on her records? That's not an aesthetic affectation. That's just her. She makes the "Mind the gap" voice sound gushing.

But back to the New Year's gig from hell. By the chorus, she had a voice again - or at least, she did to the viewers. Her own sound levels never normalised.

"Where I was standing I literally had no vocals," she explains. "I had nothing to pitch against." (As she warms to the story, her voice contains a note of passion just discernable to the human ear.) "It was like singing with a Walkman on." In the footage she looks as flawless and controlled as ever, though her eyes do flash Insane Anger occasionally - but fortuitously, the song, "Catch Me", is written in the persona of a psycho stalker girlfriend, so it actually looked quite cool.

Sophie pulled it off. "I hope so," she says, slipping off her jacket to reveal a very cool Betsey Johnson Victoriana-style dress, draped over a very skinny body (of which more later). There was just one more contretemps that night.

"Richard went up to the sound man, who just shrugged. Richard was so angry he threw his drink over him. A very un-Richard thing to do." Chivalrous Richard is her new husband, a bassist with an extravagant comb-over. (They look adorable together in pictures, with their matching long legs and pale bony faces.) His band, The Feeling, produced those catchy-cutesy numbers that blocked the airwaves last year: "Fill My Little World Right Up" and "I Love It When You Call", but we won't hold that against her.

It has been a dramatic few years for S E-B. First she split up with Andy Boyd, her long-term partner and manager, 11 years her senior. Professionally she has excelled without him, getting the pied pipers of pop - Cathy Dennis, Xenomania, Fred Schneider - to work with her in calling tunes on her new album, Trip the Light Fantastic. She wrote "about 80 songs" and then whittled it down to her favourites. The video for her single " Catch Me" was directed by Sophie Muller (who does simply eh-veryone's pop video, from Mika to Eurythmics). The idea sounded iffy to me: a pop synth homage to Don't Look Now, featuring S E-B prancing round Venice in a red dress. Oi, you with the cheekbones, leave my favourite film alone! But then I watched it.

It's fantastic: witty, sinister, gorgeous. Look it up on YouTube now! (I'm not on some kind of retainer, you know. Honest.) Perhaps it's so good because S E-B performs it all with absolute earnestness. And to take pop frivolities that seriously is pretty camp. No wonder she goes down so well at GAY. "I love the cartoony, larger-than-life side of what I do. It's just all about having fun, isn't it?" she says in that flat, joyless voice. The gap between the meaning and the delivery is big enough to build a career in.

Soon after the split from Boyd she started dating Richard, who'd been her bassist on tour, and a friend of hers for a while. It seems to surprise her still.

"When people tell me they've fallen for someone they've known for some time, I was always like, 'Hmm, that doesn't sound right.' Now I've done it myself." Less than two months into the relationship she found she was pregnant. She and Richard still hadn't really told anyone - including fellow band members - that they were an item. "It was a case of 'Guess what, we're together and we're having a baby.'" (Her deadpan delivery comes into its own here, I'll admit.) It was clearly the happiest of accidents for her. "My mum had me when she was 23 and I suppose in my head I always thought I would love to have a baby at that age."

When her mother, the TV presenter Janet Ellis, had a baby - Sophie's younger brother Jack - out of wedlock, the Blue Peter community was scandalised. But in the pop world it's positively de rigueur. "When it happened I was 24 and it just felt right." But during pregnancy she was rushed to hospital with pre-eclampsia; her son, Sonny, was delivered eight weeks early. He was in intensive care for five weeks; later, at four months he was re-admitted with meningitis. "It was just so scary, I don't like to think about it," she has said. He made a perfect recovery, though. He went to his parents' wedding in Umbria when he was eight months old. Now almost three, the little mite seems to be living it up, in fact.

Today he's gone to the supermarket with blue eyeshadow on, apparently. " He was sitting on my lap when I was getting made up, you see..." He also has, by the sound of it, a fancy-dress wardrobe to rival Elton John's. "He's got his complete Care Bear outfit, his Christmas pudding, his dinosaur, his cowboy suit, and ... oh yes, his Happy Feet penguin costume. His everyday clothes are quite dandyish. Corduroy trousers and braces and things. I love it. What's the point of having them if you can't dress them up in cute outfits?"

Conversation segues into finding a school for Sonny. "I'm looking to send him to a state school round here - not one where the kids' parents are all in the media."

Is that a political choice too? "I was brought up to be, you know, a staunch Labour supporter, all Conservatives are evil, that kind of thing. But when you go and visit schools it does test you. Because you want what's best for your child and if you go somewhere really multi-racial, well, that's great, of course, but not so great if everyone else in the class has English as a second language, because he's naturally going to get less attention ..." But didn't she herself go to a rather plush private school? "After state school, yes. I found it a real shock when I started Godolphin and Latymer. The teacher called out the names and she was saying 'Rubeque' and I thought it was a really posh girl's name and it turned out she was just saying Rebecca. I got paranoid about stuff. Lots of them had horses and one was wearing a cape. I felt really out of place."

The other girls weren't very nice about her appearance, one hears. Apparently they called her "rhombus-face". (A private school insult if ever there was one. She'd have been plain old "50p-face" anywhere else.) Sophie says it wasn't her looks so much as her weight. Too podgy? "Apparently so. You know you get these real bitches in your year and they find your spot and dig their heels in." Oh dear. Has that contributed to her super-skinniness now?

"I've been tinier. When I was 20, 21, I was this size. It was more to do with coming back from motherhood. I wanted to feel like I owned my body again, because you do give yourself over to it, to pregnancy and breast-feeding. I spent six months being Sonny's mum and not thinking about my body or fashion or anything.

"So then I emerged, and I started going to the gym. I don't do diets at all. I think there's nothing more boring and anti-social than sitting down and saying, 'I'm not eating that.' Would you like to try some of my salmon salad?" She proffers her plate, stretching those feline eyes wide. I suddenly remember I'm talking to Sophie Ellis-Bextor. She is very good at normal chat, for a popstar.

She seems completely straightforward and is rational and grounded in a way that most stars could only dream of. "I figure this album is really important to me, 'cause if you have a successful third album, you have a career." By now, I've even got used to her voice sounding as passionless as a waitress reading the specials. In fact, it's beautiful, in its own way. Certainly it's good for sarcasm. She hasn't heard about the recent Blue Peter competition-rigging scandal (like, where has she been? America, actually) but when I explain she archly declares herself " shocked. I'm Shocked of W10."

I suppose we have to bear in mind that this is the girl who pinched Blue Peter badges from her mother and flogged them in the playground. Not a goody two shoes. Though she likes two good shoes, right enough. Her collection numbers about 160 pairs; her favourite shoe shop at the moment is a vast store in Hamburg. "I suspect it's for transvestites, as the sizes go up to about a 10." She has also conceded, finally, to getting a stylist. "Actually I love it. When I used to do it all myself I'd be stood in my bedroom at 1am with all my outfits laid out, thinking, 'Now, tomorrow I've got two tellys and a performance...' I just don't have the energy for that now I've got Sonny." She still takes a keen interest, though. "I have a gander at Catwalking.com and go on Ebay. And I just found some pea-green jeans I'm really into!"

Her voice ringing with emotion, she leaps out of her chair and high-fives me. No, you're right, she doesn't. She sits there as icily, gorgeously composed as ever. I wonder if she ever loses it. Where, how, when? " Having a really good dance is my release. I definitely go loopy if I haven't had a night out for a while."

Her favourite spots are gay clubs like Rebel, Rebel, and the night Wig Out at the Ghetto Club. Can she go there incognito? "Hmm, me incognito? Not in a gay club. Once when I went there they played 'Murder on the Dancefloor' and I was standing in the middle and everyone was singing it to me with these great happy faces. It felt like I was surrounded by lots of new friends. It was just like the end of a film when the credits are rolling." The calm, the cool, the preternaturally collected Sophie Ellis-Bextor, ladies and gentlemen, starring in the movie of her life at a cinema near you.

The single 'Me and My Imagination' is out on 7 May. The album 'Trip the Light Fantastic' is out on 21 May on Universal Records