UK- [News of the World] Heather Mills cheated on Sir Paul McCartney for SIX months with a secret lover, the News of the World can sensationally reveal today.

Our bombshell exposé of her secret betrayal explodes as the couple prepare for a showdown week in their bitter multi-million-pound divorce battle.

We can reveal that Mucca romped with handsome film editor Tim Steel THE NIGHT BEFORE joining Macca on a romantic Caribbean Valentine’s holiday.

The one-legged ex-hooker even brazenly showed her lover Sir Paul’s tender texts—before leaping into bed with Tim for marathon sex sessions.

“I didn’t mind—I suppose I was flattered that Heather still wanted to have sex with me despite being pursued by this musical demi-god,” says Tim, breaking his silence on an affair that will stun the nation.

“Heather was insatiable between the sheets and she liked to call me her four-times-a-night guy. Our record was six.

“Most of the time it was multiple orgasms. Heather has a very unusual erogenous zone—her stump. I used to massage one particular sensitive area of it and give her an orgasm!

“But it was strange lying in bed talking about Paul McCartney. I would be with her when he called or texted her. She’d even show me the texts!”

Leeds-born Tim’s shocking account of their affair will deal a heavy blow to 65-year-old Macca’s pride—and put a time-bomb under Mucca’s bid to squeeze an £80million pay-off out of the pop legend.

She even confided in her lover as she decided whether or not to commit to Paul.

“Marriage to him opened lots of doors for her—and that’s the only reason she did it,” says Tim, 45. “She falls in and out of love with men on a whim and she messes with your brain.

“When she bedded me for the first time it was in her fiance’s flat! She was that kind of girl.”

Tim had already been seeing Mucca—then a model turned charity campaigner—on and off for three years when Sir Paul fell for her at a bravery awards ceremony in May 1999. The star started dating her in August.

“I’d been working abroad for a few months and was surprised when she told me she was dating Paul McCartney when I got back in September,” says Tim.

“When we met up it turned out to be the same vegetarian restaurant down in Hove where HE had been taking her on dates.

“Paul even sent Heather a lovey-dovey text as we ate. She showed me it and casually quipped, ‘I’m being pursued by a Beatle’.

“We both had a good laugh about it and then we went back to the house she shared with her sister Fiona and had sex—and as usual it was mind-blowing.

“My friends would ask me what it was like with a woman with one leg and I’d tell them, ‘No different to making love to a girl with two legs’.

“I’m a fit guy but she had tremendous stamina. We’d be at it like rabbits. She was up for it anywhere too. Once she gave me a bl** j** under the desk while I was working in my editing suite. And on a holiday in South Africa we stripped and made love in the shelter of a sand dune—even though tourists were watching.”

The two were leaping in and out of bed behind Sir Paul’s back right up to the Valentine’s holiday the smitten star planned for them in 2000 on the private island of Parrot Cay.

The star was already out there in an £8,000-a-week beachside cottage when Heather, now 40, headed to Tim’s London flat for a night of lust before flying out to join him.

“I was glad she wanted to stay with me,” says Tim. “She was in two minds about him and was wondering if she was doing the right thing.

“She seemed nervous about this first holiday with him.

“Then we made love and, as always, the sex was very good. In the morning she kissed me goodbye.

“She went straight from my warm bed to the airport.”

It was the last time they made love, but duped Paul will be shocked to learn Heather’s close friendship with Tim continued through their 2002 engagement in India and beyond.

It was Tim who edited the couple’s private home video of their time in India which Heather gave to Paul at his 60th birthday in 2002.

Tim admits: “I guess I hung around because I really didn’t think Heather and Paul would last. He was an old bloke and I knew what Heather was like. She was only in love with what Paul could do for her. She loved the idea of being Lady McCartney.”

Tim first met Heather on a blind date set up by a mutual friend in August 1996. “It was love at first sight. I was bowled over,” he says.

At the time, Heather was already engaged to tennis organiser Marcus Stapleton—but that didn’t stop her getting what she wanted.

She took Tim back to the Regent’s Park mews flat she shared with Marcus, who was away on business.

Tim says: “We lay on the bed and kissed and fondled. She wanted to have sex but I didn’t think I’d be able to manage it because I was so nervous.” The next day divorced Tim met up with Heather to walk her Wheaten terrier, Oliver in Hyde Park. He recalls: “She looked stunning. She was wearing those sexy lace-up boots she wore on the cover of her book Out On A Limb.”

They made love for the first time a few weeks later—in Marcus Stapleton’s flat. “Heather instigated it with a nice bit of oral sex then we went all the way,” says Tim.

“There was never any awkwardness about her leg. She would take it off the same way she would a pair of slippers.”

Their sex life continued throughout the next three years of their on-off relationship—even when they were seeing other partners. Tim reveals: “We discussed it and decided to keep our relationship a secret. I would stay in the background.

“It was all sex—I’d come home from work to find her waiting for me naked in bed. If ever I was too tired for it, Heather would get angry and kick me out of bed. She’d tell me, ‘If there isn’t going to be any sex, you can sleep on the sofa’.

“She had a hoard of vibrators of all shapes and sizes for when she was home alone. Her favourite was a huge back massager that she plugged into the mains.

“My mates always used to joke that they knew when I was away on business because the lights in London dimmed!”

In August 1997, Tim and Heather moved into a flat in Streatham together. But outside of the bedroom, life with Heather was far from bliss. Tim struggled to understand her furious temper.

He says: “The first time she exploded was when we were in South Africa on a holiday and I’d criticised Mel Gibson’s role in the movie Ransom one night. Heather didn’t agree and we had a blazing row. She packed her bags and flew home.”

They split three times during their tempestuous secret relationship.

Tim—who now lives in Australia—says of this week’s up-coming High Court divorce battle: “Heather will fight Paul tooth and nail to get what she wants.

“I know her better than most. She’s going for the jugular and won’t shy away from fighting dirty to win.

“Something that could have been the best thing that ever happened to her has now turned round and bit her on the a*** big time.

“If she’s got something on Paul, she won’t hesitate to use it to her advantage. With a click of the fingers, she can switch from smiles to tears.

“I hope Paul and his legal team know what they’re up against and are ready for her.”