He is 'crushed' he has no legal claim over boy he still considers his son

The father was also conned out of more than £100,000 in support the child

For any father in his 50s, the birth of a healthy son must feel like quite a miracle, a lucky final shot at the sort of family life more normally enjoyed by younger men.

So when, nine years ago, Jonathan Whiting became a dad for the third and final time, he threw himself into fatherhood with all the pride and enthusiasm you'd expect.

Today, sitting in his smart home in the South of England, he speaks about his young boy lovingly and with passion. Books and toys are neatly stacked, ready for use.

Yet there is something glaringly absent from this particular father-son relationship – and that thing, disastrously, is the boy himself.

Last week, Mr Whiting, a university lecturer, found himself at the centre of one of the most extraordinary paternity cases ever heard in a British courtroom, one which has fascinated and appalled the public in equal measure.

It is the heartbreaking story – first revealed by The Mail on Sunday earlier this month – of a devoted father who discovered his ex-wife had duped him into spending six years bringing up a youngster as his own when, in truth, the boy was fathered using another man's sperm.

Jonathan Whiting - which is a pseudonym - was tricked by his ex-wife who duped him into spending six years bringing up a youngster as his own when, in truth, the boy was fathered using another man's sperm

'She lied repeatedly about the paternity for five years after our separation so that she could keep receiving the huge maintenance payments while keeping up a secret family life with the boy's biological father,' he says, speaking for the first time about his disturbing ordeal.

And now he has lost his son, aged nine, possibly for ever.

Jonathan Whiting is not allowed to identify himself, or the boy, and this is not his real name. Yet he is determined to tell what happened to him and to explain how his former wife deliberately lied and plotted to create a handsome 'designer baby' by IVF with a former boyfriend.

In the process, Jonathan was conned out of more than £100,000 in supporting the child.

He describes her as a wealthy woman, obsessed with money and motherhood, who lived in a moral vacuum and would stop at nothing to fulfil her fantasy of having a child with another man – but having Mr Whiting pay for it.

Just a few days ago, he won a landmark court battle when a judge upheld his claim that his ex-wife had fraudulently deceived him, in what is thought to be the first paternity case involving an IVF baby in Britain.

He was awarded about £100,000 in damages and costs, while his former wife was branded a liar. But it is a pyrrhic victory. The reality, he says, is that he would much rather still have a relationship with the bright, energetic son on whom he doted.

'I have two older children by my first marriage, but it's always there at the back of my mind that I have another child out there who will grow up without me,' he says.

We are in the sitting room of the neat detached home that he shares with his current wife, in an unremarkable area. He is lean and youthful looking, despite his 60 years, his nervous energy causing him to unexpectedly jump up and pace as we speak.

But there is no doubting the pain he still feels over the loss of his son.Struggling with his emotions, Jonathan says: 'When people ask how many kids I have, it cuts me to bits.

'I say that I definitely have two, or I'm not sure. I can't see children of his age without crying. I think about him all the time. I still love him and I always will.

'We were unspeakably close. I was his dad in every way. Even after his mother and I split up, I saw him several times a week.

Whiting is determined to tell what happened to him and to explain how his former wife deliberately lied and plotted to create a handsome 'designer baby' by IVF with a former boyfriend

We played football and hide-and-seek and went to the park like all dads do with their sons. He is a gorgeous, good-natured child, who loves books and has a great sense of humour.

'I imagined his future with me in it and I was so proud of him. But now I have no claim over him, no rights. My entire world was crushed and the word 'loss' is too shallow to describe what I felt.'

He insists that although he bitterly resented being conned, the case was never just about money. His face flushes red as he battles to hold back the tears. 'I still have his toys and books in my house. Whenever I look at them I feel sad.

'This morning, his cat toy fell on the floor and made a meowing noise and I nearly broke down. Just that sound brings back so many memories.

I imagined his future with me in it and I was so proud of him... But now I have no claim over him, no rights. My entire world was crushed and the word 'loss' is too shallow to describe what I felt Jonathan Whiting

'It was as though my son was ripped from me and sucked into a black hole – like she wanted to pretend he had never existed. But I will love him for ever and nothing will change that.'

For the past couple of years, he has been allowed only a few minutes of contact with the boy he still thinks of as his own.

Thanks, he says, to a wrong-headed legal loophole, a woman who carries a child – regardless of its DNA – is the legal mother, while a man who has no biological connection (but is on the birth certificate and other legal documents) has no claim at all.

It was certainly not the future he imagined when the couple met at a singles' date night in a London wine bar, back in 1998. 'I could sense a different energy around her,' Jonathan recalls. 'She was pretty, with long dark hair and radiated such enthusiasm. She seemed especially interest in my work.'

Jonathan admits he was too easily seduced by flattery. 'It was a head rush. It made me feel good to have someone so totally focused on me.

'She had a lighthouse way of making me feel that I was the centre of her world.

'I was intrigued, and that's how she managed to snare me.'

Susan – again, not her real name –was in her late 30s and very career focused. Her job meant she travelled a lot and often did weekend overtime.

'She came from a financially comfortable middle-class family but was obsessed by money and the need to save it,' he says.

She took his number and called him two weeks later. The courtship progressed quickly because, by his own admission, neither were in the first flush of youth and both had failed marriages behind them.

He was not long divorced from his first wife – with whom he had two much older children – after more than 20 years together, and Susan, for her part, had finished with a relationship of her own. They wanted 'something meaningful' and made a peculiar pact not to have sex until they had at least '30 hours of contact'. They made it to five dates.

Jonathan found her different to the other women he knew. 'She was very bright and really good at making a man feel very good about himself,' he says. 'She was also fun and I had no defence when she turned up the wattage of her charm. She got me hooked very quickly.'

Susan had been sharing a house in South-East England with an ex- boyfriend, but within three months he moved out and Jonathan moved in. He now concedes that it was 'much too soon'.

Susan, who was then working for a large company, began to steer the relationship towards marriage. He proposed to her in Prague with a Powerpoint presentation of the '100 things' he would do to express his love – they included 'washing your car' and 'having fun together'.

The only sour note to the occasion, he recalls, was her demand for an engagement ring costing more than the £1,000 limit he had set.

Having acquired her ring of choice, Susan began to push for them to have a child.

She was very bright and really good at making a man feel very good about himself,' he says. 'She was also fun and I had no defence when she turned up the wattage of her charm. She got me hooked very quickly Jonathan Whiting

'I already had children, so I didn't have an overpowering need to have my DNA reproduced,' Jonathan says. 'I'd had a vasectomy but she was desperate to be a mother and I wanted her to happy so I went to a specialist who said he could reverse it.'

Initially, however, they tried artificial insemination with donor sperm in 1999 and 2000. This was followed by a failed attempt at surrogacy in 2001. Each failure seemingly sent Susan into what Mr Whiting describes as a mild depression. She threw herself into work, setting up her own company.

This clearly put a heavy strain on the relationship. Jonathan resented the fact that she no longer 'focused on him'.

He hoped things would improve after they were married in 2002. But, to his chagrin, her level of commitment to the relationship seemed to plummet. 'We were living in a palatial five-bedroom mansion, but we saw little of each other,' he said.

They tried couples therapy and Jonathan even suggested a trial separation, which he now wishes had happened.

'With hindsight, I should have walked away on so many occasions, but I didn't want another failed marriage,' he explains.

The pair had been trying for a baby for five years – including a painful reversal of Jonathan's vasectomy – when they visited an IVF clinic in Barcelona for one last try at being parents. This time, they planned to use his sperm and a donor egg which would be implanted into his wife for the pregnancy.

In September 2004, Jonathan flew to Spain and made his sperm deposit, but when Susan returned four months later to have the donor eggs fertilized and implanted she went alone – or so he thought. Only later did she reveal to him that she had in fact gone with her ex-boyfriend.

Jonathan knew the pair had remained friends and had briefly met the man once. But he had no suspicion that the boy he considered his son was the boyfriend's baby or that after the birth in 2005 the two played 'happy families' behind his back.

'I believe she wanted a kind of designer baby using her ex's sperm because he was really good looking and she hoped he would get back with her,' Jonathan says.

'I was a hands-on dad. I think I did at least 40 per cent of the nappy changes and almost half the overnight feeds. It was fantastic being a dad again, but Susan was impossible. We were constantly arguing about the right way to do things for the baby. She would say, 'It's my child' and ultimately I couldn't live with her any more.'

I was a hands-on dad. I think I did at least 40 per cent of the nappy changes and almost half the overnight feeds. It was fantastic being a dad again, but Susan was impossible. We were constantly arguing about the right way to do things for the baby Jonathan Whiting

Today, he takes a clear view of why she did this: having achieved her dearest wish, Susan didn't really want to share.

The boy was seven months old when Jonathan moved out. Over the next five years, however, his former wife compounded the deceit by demanding a generous maintenance agreement after their divorce. It was not until 2011, when Jonathan made an application for more contact with the boy, she finally revealed he was not the father – by text.

After a DNA test, a devastated Jonathan struck back with a legal claim. 'I just couldn't live with the idea of her getting away with such wicked deception,' he says.

As for her ex-boyfriend, Jonathan has nothing but disdain for the man who has taken his place and who he says 'hid behind the veil of her deceit'.

Jonathan has since remarried, but says that he has been left with deep psychological scars. 'Every time I see a child his age, I feel affected.

'The hardest thing is knowing that he's still out there and I just have no claim over him,' he says. 'He might think I have abandoned him – one day I was there, the next I wasn't.

'What makes me most angry is what's been done to a child so precious, one that she was so lucky to have. I was allowed less than a minute with him on his birthday last year and about six minutes with him on his doorstep this year. It was long enough to give him a football kit and a hug before he was dragged away.'

He points out that the boy had grown close to his extended family. 'My two older children and step-children adored him.'

The judge awarded £40,000 to cover the impact of the six years' deception, loss of earnings and maintenance, plus £60,000 costs.

Jonathan did not recover all the child maintenance he had paid because, the judge said, he had enjoyed the relationship with the child while he believed him to be his son.

After all that, it seems almost incredible that Jonathan had offered to settle the claim last summer for £12,500, including his legal costs. However, Susan had refused that offer. 'I was naive and foolish but I never dreamt anyone could do the things she has done,' he says now. 'But I was his original father and I hope to have given him some basic stability. I hope some of those pillars will remain with him.

'I know it's unrealistic, but in my heart I would like to keep in contact.'