X Factor's Sam Bailey is performing at Cornbury Festival

Singer Sam Bailey laughs as she tells me about the night she won X Factor.

It wasn’t just her family and friends rooting for her, it seems. So were the inmates of HM Prison Gartree— where Sam worked as an officer.

The hardened lags at the Leicestershire nick — whose list of former hardcase inmates includes Reggie Kray and Ian Brady — had cheered Sam along and reacted to her victory by hammering on their cell doors.

“When I won, the whole prison was banging on their doors,” she says. “It was as if there was a big football match on and someone had scored. All had a bit of approval for me — though some took the mick, of course.”

She is talking from her home, a typical three-bedroomed semi on the edge of Leicester, which she shares with her husband Craig and children Tommy and Brooke. She is expecting her third child, and admits life is busy.

“I’ve decided to take a day off,” she says. “It’s nice to have a bit home time. It’s been a little bit hectic lately, but that’s all part and parcel of putting myself in the spotlight.”

Sam’s achievements are outstanding. After winning the tenth series of the BBC talent show, her debut single, a cover of Demi Lovato's Skyscraper, made the Christmas number one slot — the first by an X Factor star for three years. Then earlier this year she supported Beyonce for a UK date of her Mrs Carter Show World Tour. Her debut album The Power of Love debuted at number one in the UK Albums Chart in March.

“I have been very lucky,” she says with delight. “I’m still doing alright and have fans begging me to play.”

Though she was launched by X Factor, Sam, 36, has years as an artist. She formed her first group, the ska duo Girls Next Door, when she was 18, and is a former Pontins ‘bluecoat’ and cruise ship and club singer.

“I’ve been doing it for so long,” she says. “I don’t get nervous, I get a buzz. The more people watching me the better. But I never thought for a second I’d even enter X Factor, let alone win it.

“There are so many knock-backs in life, I’m used to it and wasn’t worried. I have been told ‘you are not what we are looking for’ so many times in my life, I am immune. But I have an appreciation of everything. Just being there was enough. It just goes to show what’s around the corner.

Her debut headline tour kicks off early next year, but before that she has a summer of festival dates — including one on our doorstep at Cornbury. Sam plays the gathering near Chipping Norton, on July 6.

Is she worried about playing live while pregnant? “I’ll be seven months then,” she says. “I was pregnant before when I was singing in a band, and I worked then until I was ready to drop. When you’re singing you know what you can and can’t do. People think you’re going to squeeze the baby out on a high note, but that’s not the case.

“One day I’ll tell her all the stuff that happened, the places I performed, when she was in my tummy!

“I didn’t want to take a career break. I still want to be a working mum and earn money for the kids. Luckily I’ve got a husband who’s very domesticated. There’s not a day when he’s not hoovering. He’s a nightmare sometimes!”

Sam has the kind of no-nonsense approach to life you’d expect from a prison officer. She tells me she discovered she was pregnant after taking a test in the toilets of her local Asda. “I knew I was pregnant anyway,” she says. “I know the symptoms but needed to find out, so when I was at Asda I went to the toilet and did a test. It holds a special place in my heart now!” she jokes.

She refuses to let success go to her head. “What’s the point of buying a half-amillion pound home? In a year I might be forgotten about and stuck with a mortgage I can’t afford. People say ‘you’re famous, you don’t have to worry,’ but I think about the inevitable. I know previous X Factor winners have gone back to being normal and have been forgotten.”

“It’s good to keep myself in the public eye but also show I’m a normal person. I live in a normal suburban semi, I go shopping, and I go to the park. I like pie and chips with lots of vinegar and enjoy staying in with a DVD. I don’t want to go to posh restaurants — I’d rather have a pub meal. I don’t want to pay £38 for a starter that’s smaller than my dog!”

And she continues to enjoy life well away from the showbusiness glitz, in the unremarkable, though friendly, suburb of Leicester Forest East.

“My neighbours have all been really cool,” she says. “Every week I got through on the show one neighbour cooked me a chocolate cake. And for the final I got strawberry!”

One thing she can’t do is return to work at the jail. “I could never go back to that as the inmates know too much about my personal life,” she says seriously. “You don’t give much away when you’re an officer. There’s a barrier you don’t cross. The people there see me in a different light now.”

But, despite her suburban lifestyle, Sam is proud of her music industry friends — not least 17 year-old X Factor runner-up Nicholas McDonald. “I’m like a mother figure for him,” she says. “I have to keep it hush hush when he comes round though, otherwise there’d be queues of screaming girls outside the door!”

Though next year’s headline tour — which includes a date at the New Theatre, Oxford — looms, for now though her sights are set firmly on Cornbury, where she stars alongside Jools Holland and Simple Minds.

Cornbury Festival
Great Tew Park
July 4-6
Adult weekend camping tickets are £200 (VIP £310) from cornburyfestival.com

“I’m looking forward to it,” she says. “And I’m taking a trip to Bicester Village while I’m there. It’s my idea of shopping heaven!”