They met 25 years ago through David Van Day, one half of the singing duo Dollar, whom Lesley was dating at the time. The other half, Theresa Bazar, had her hair cut by Nicky.
"We didn`t click immediately though," says Lesley. "He had short hair when we met and a moustache, a pink bow tie, balloon trousers worn with braces and black patent shoes.
"It wasn`t what you`d call love across a crowded room.
"One day he asked me, `What are you doing tonight?` and I told him I was going to Tramp with some friends. He suggested picking me up as he was going as well. "But he was four hours late and by the time we got there my friends had gone. That was our first date."
They married on impulse the following year in Las Vegas.
Ten years later in 1991, when Lesley had given up her job in fashion to devote herself to being a full-time mother, disaster and opportunity struck.
Nicky lost his job at John Frieda after a row. It was Lesley who came up with a rescue plan for the family and set about finding a salon so Nicky could branch out on his own.
"It was a huge gamble," she says. "I had two babies and no income. My son learned to crawl and walk on bare floorboards and we sat on deckchairs. We couldn`t afford furniture."
Helped with £80,000 in loans ? a fortune then ? they found a smart salon in Mount Street in Mayfair.
"We filled it with antiques ? they were all borrowed," Lesley recalls. "The night before we opened, we were both there cleaning and scrubbing until two or three in the morning."
Nicky`s talent was quickly recognised and he became the most famous and sought-after hairdresser in Britain. His client list included royalty, pop stars and models.
The Clarkes could call the Duchess of York, Brad Pitt, George Michael, Gwyneth Paltrow and Martine McCutcheon personal friends.
In 1997, Nicky and Lesley finally bought a dream home ? a six-bedroom house in St John`s Wood in North-West London, near Lord`s cricket ground, where they could bring up their family.
They had been in the house for just three days when she discovered his infidelity.
He immediately agreed to stop seeing Susie Bick, a beautiful Vivienne Westwood model, who later married Australian singer Nick Cave.
"But the trust was broken," Lesley says quietly. "It changes your inner fibre. You start to question yourself. I asked how I could have been so wrong in my judgment of somebody I love."
At first, they tried to work round the indiscretion. They went to see a therapist together and, for a few weeks, things seemed fine.
But for Lesley, there was no going back. It seems that Nicky, too, was filled with regret.
"We didn`t tell the children what had happened immediately," says Lesley. "We covered it up because we didn`t want to hurt them and wanted them to keep their innocence for as long as possible.
"When we did tell them, they broke down and cried. It was awful."
The more reserved of the two, Lesley struggled to cope.
"I don`t jump into friendships," she says. "But once I`m in a friendship it`s for life, which I expected my marriage would be. I`m not bitter about it, but I don`t think one ever gets over betrayal of that magnitude."
Looking back, Lesley had a feeling that something might be wrong within her marriage. "A big distance seemed to come between us at the time," she says. "I think we thought it would just work itself out."
Over time she has been able to put matters into context. Much as Nicky`s affair was to blame for the break-up, Lesley says there were other factors.
These days, with her faithful black labrador Blossom lying at her feet, Lesley can afford to relax. But things were not always that way.
"Our marriage broke down partly because I was working 18 hours a day," she admits. "I was exhausted. I was doing the accounts. I did the PR for the salon and the marketing for the company.
"I even worked on reception and did the cleaning when we first started.
"At midnight I`d fall into bed, but I had to get up again at six to get our two children up and give them breakfast. Nicky probably felt he was neglected."
In retrospect, she also feels she was unduly influenced by the therapist they were consulting. Within a few weeks of Lesley discovering the affair, the therapist told her to dump Nicky because all was hopeless.
She was still in shock, she says, so she agreed. "The therapist said: `What are you doing, you must leave him,`" Lesley explains. "So I did.
"I was in such shock and pain that I wasn`t thinking clearly at all. It was all very confusing.
"I made lots of stupid decisions at that time and that was one of them ? totally out of character."
Devastated as she was, Lesley had precious little time to sit still. "I had two children to look after and the business to run, so I didn`t have much time to wallow in self-pity.
"There`s no way I would have failed the children or the business. I just threw myself into looking after the kids and doing my work."
So little time did Nicky and Lesley have to spend on their home life, in fact, that inertia almost kept them together. For six months they continued to share the St John`s Wood home without any great discord.
So, in typically forthright style, Lesley took matters into her own hands. "I found him a flat and moved him in when he wasn`t here. I just moved all his stuff and gave him the key," she recalls.
Even now, their arrangement is unusually close. Nicky has bought a house only five doors away from Lesley. Each August and Christmas they holiday together with their son, who is studying at Leeds University, daughter, who is on a gap year, and Nicky`s 85-year-old mother.
Lesley has recently bought a home in Majorca which they all share. "I`ve got the front room with the sea view and he`s got the back room with shower," she says with a smile. "He likes showers.
"Every Christmas we visit New York with the children, but we spend Christmas Day together at home in London and I cook.
"The children have seen their daddy every other weekend and he`s been nothing but a good father. I made sure it didn`t affect them. I swallowed things.
"I didn`t let them find out any details. I just kept lots of things hidden from them."
But there is one golden rule when they get together with the children. Any new partner on either Nicky or Lesley`s side isn`t allowed to join them.
"When we`re on holiday as a family, we`re a family," she says.
Nicky is currently dating Kelly Hoppen, the interior designer.
"I`ve never met any of his girlfriends, even though he lives five doors away," says Lesley pointedly.
Their continuing attachment is emphasised by the fact that the Clarkes have not bothered to divorce.
"Why should we? I don`t want to get married," laughs Lesley. "And he`s always said he doesn`t want to get married again. But things might change.
"We still have a joint bank account and we own everything together, including the property. We haven`t split anything.
"I pay half of his household bills and he pays half of mine. It may seem like an extraordinary situation to some people, but that`s what we have done for ten years now.
"I handle all the money and I see him several days each week because of the business. We do have mutual friends still, so they`ll invite us and we`ll normally go out together.
"But we also have separate social lives. I`ve got my own social circle, which is quite different from his."
Nicky`s friends tend to be celebrities, while Lesley`s are in fashion and charity. "I`m very shy with strangers and Nicky`s not," she says.
"He`s very outgoing with strangers. He`s more amiable and will talk to anyone."
She admits: "I`m more stay-at-home and Nicky`s more social and loves going out for dinner. He really loves his life, although not all his friends are celebrities.
"He does have some old friends who are normal as well.
"We still love and respect each other. He just told me yesterday that he loves me more than anything in the world. And I love him.
"But I could never share a home with him because I`ve been on my own for such a long time.
"It`s like having a marriage, but not. I can have him in the summer and at Christmas, but then I`ve got my freedom the rest of the time."
Lesley, who confesses that she does find the arrangement odd, describes their relationship as more "brother and sister" than man and wife.
She admits to having had some famous boyfriends, and adds: "I do pinch myself if ever I get down or feel unhappy, wistful or reminiscent. I just remember a time when I couldn`t even buy a pair of shoes."
These days, she is often asked for her advice by girlfriends. "I say, it`s easy to walk out on a marriage, but it`s hard to make your life work after that. So be sure that, if you leave, it`s what you really, really want.
"I`m very privileged and I`m very happy. But I would have preferred to have been with my husband and the father of my children. So I`m making the best of things."