All in her stride

She and her husband, artist Graham Swift, 31, who have homes in London and East Yorkshire, were joined by baby Billy Percy Harvey just three months ago.

Sarah's delighted with her son and full of the wonders of how biology works.

"I thought computers were clever, but nature's really got it sorted," beams the 32-year-old.

And she's just so calm about it all. She's not one of those new mums who can only talk baby. Nor is she one of those celebs who won't discuss the new addition and only wants to talk work.

In fact, Sarah's so laid back that the fact she can now add mum to a list of skills that already includes TV presenter, property developer, writer and internet entrepreneur, has almost escaped her.

"Am I a mother?" she questions, seriously. "I guess I am! It's not a big life change like getting a new job or moving house, which is a huge upheaval. It's a slow progression and that's rather nice.

"I don't feel that different. I've got a cat who I really adore and all that's happened is the cat's been down-graded and Billy's taken his place. I don't like Billy more, it's just that I don't like the cat as much," she laughs.

"I thought I was going to be a terrible mum, have a nightmare child, not to like it at all, to hate it, to find it inconvenient, for the whole thing to be a disaster," she admits. "And actually it's rather gorgeous."

This is helped by the fact that little Billy appears to be an unusually good baby, although Sarah admits she's currently suffering from 'mother blindness'.

"I geared myself up to the fact that I'd have a screamer," says Sarah, who goes on to explain that serene Billy, who's sitting quietly in a buggy beside her, is quite the opposite.

"I think if you have high expectations of yourself then it would be very hard having a baby," she adds. "But I had extremely low expectations of my mothering skills and I've excelled myself!"

She even took labour in her stride, despite suffering for far longer than the nurses at the Chelsea and Westminster hospital would give her credit for.

"They only counted 24 and I counted 48 hours of excruciating pain. They told me to go home and sleep and I was like 'I'm dying, I need drugs!'. I had loads of them in the end, poor Graham had none - just 40 cigarettes and a few sneaky pints," she jokes.

Motherhood has seduced her, got her hooked and now she's craving more.

"I want another 10," she says. "But you never know, some people can't have another one. And I might not get a good one next time."

It's this kind of brutal honesty that's made Sarah such a hit on Channel 4's Property Ladder, the new series of which started on Wednesday with a feature on a house at Sandbanks.

Her pregnancy coincided with filming the fourth series of the show that's made her a household name, which meant working long hours.

"It was quite tiring. I worked up until five or six days before I went into labour. I had a big bump but it was an easy pregnancy - I wasn't sick or ill. I'd like to say that was down to good skills but it was luck of the draw. If it had been a horrible time it just wouldn't have been possible to work so much.

"Now I do shorter days so I get back to see Billy in the evening, and having a nanny helps."

Sarah hasn't had the luxury of being able to turn to her own mother for advice, having lost her mum to cancer when she was just 10 years old.

"I feel very sorry for her because it would be very hard to know that I was going to leave Billy. And she knew she was dying. That must have been really awful. I haven't really thought about it from that aspect before - it was all 'Me, me, me'.

"Her name was Ann Harvey Kay and I wanted to use her name somewhere, so I used Harvey. Graham wanted to call him Percy as a first name but I'm not sure about it, I think it's a bit like Apple."

Her architect father, Richard, 64, remarried and Sarah's very close to him and step-mum Boo.

It's a tight-knit family - her brother Diccon, 36, is married to Graham's sister, Caroline, 36. The two couples and their children (Sarah has two young nephews) live opposite each other in south London.

It's a well-known fact that the four run a property business together. In their case, familiarity breeds success.

"It's a risky thing to do but personally I think that's why our business has lasted so long. They're my best friends, the people I choose to go out with in the evening and I get to see them in the day too.

"Like all siblings my brother and I have argued since I was tiny. I adore him. We can say the worst things in the world to each other and 10 minutes later, it's 'Oh sorry', and that's it."

She won't reveal the name of the company, or how many properties they have in their 12-year-old portfolio. But her increasing screen presence has meant Sarah's less involved in the negotiation and office-based tasks.

Not that she's been slacking since Billy came into the world. She's already filmed the latter half of Property Ladder, minus her bump, though she's taking the prospect of getting back into shape in her own time.

"I'm not there yet. I've got a stone to lose before I can get into my trousers and that will mean not eating Big Macs. But I'm doing it for me, not the cameras," explains Sarah. "I didn't watch my weight when I was pregnant.

"I'm just about to start a fitness regime," she adds.

Quite how Sarah's going to fit that into her schedule beggars belief but doubtless, she'll pull it off.

"I do run around like a headless chicken. I live in absolute chaos. My husband says I'm not capable of sitting and watching telly and gets really annoyed. Feeding Billy is the first time I've ever been able to just sit."

At the moment, she's just about managing to focus on the launch of Property Ladder.

"We choose who is going to be featured partly by property and partly by character," she explains.

"What we don't want is 12 two-up-two-down terraces because there's a limited amount you can say about them.

"And people need to be able to talk in front of the camera and have ideas so I can give my opinion."

It's fair to say that a lot of the expert advice Sarah dishes out to these wannabe property developers often falls on deaf ears. You'd imagine that would be frustrating.

"The reality is that if it was half my money I'd be a lot more fraught. I think that's why I don't find it frustrating. Well, it is a bit, but not that bad."

Property Ladder returned to Channel 4 from last Wednesday, September 22.