His role as a foster parent means Andy McNicol has had the pleasure of teaching countless young children to ride bikes and swim.

Yet each time the stabilisers and water wings came off, he felt a deep pang of sadness for the son, his own flesh and blood, who was given up for adoption at birth — entirely against Andy’s wishes.

The only memory he had of the baby, born on June 3, 1970, at Bath Royal United Hospital, was seeing a shock of red hair poking out of the blanket in which he was swaddled in his see-through plastic cot on the maternity ward.

Andy, who was 27, was forbidden by the family of his baby’s mother, then aged 22, to get close enough to see his face.

Reunited: Andy McNicol with his son John, who was given up against his wishes in 1970

When he returned the following day, the infant had been moved out of the hospital nursery.

And a few days later, Andy, now 74, heard on the grapevine in Frome, Somerset, the small town where he then lived, the heartbreaking news that his son had been put up for adoption.

‘It was the very worst day of my life, as bad as any bereavement,’ says Andy, a retired businessman who, even 47 years later, is so overcome with emotion that he has to leave the living room of his home in Walsall, West Midlands, to weep in private before continuing with his story.

‘Desperate to stop the adoption, I went straight to the local registrar’s office, where I learned that my name wasn’t even on my son’s birth certificate. Under the section for father’s name, there was just a line. I told them that I was the baby’s dad, but they said that as we weren’t married, only the mother, Brenda, had the right to provide those details, and she had said the father was “unknown”.’

Brenda’s family — angered that the child, whom she named John, had been conceived out of wedlock and that Andy was unable to marry Brenda before the birth, because he was separated but not yet divorced from his first wife — forbade him from speaking to her, either during or after the pregnancy.

So although his own mother, with whom Andy lived, had agreed to help him raise the child, he felt utterly thwarted. As he was not recognised as the baby’s biological father, he felt he had little choice but to let his son go.

Andy is pictured in 1974 with his three other children (left to right): Andrew, Lisa and Deana

Back then, British adoption laws stipulated that birth parents were not allowed to trace their offspring. Only the child, once they reached adulthood, had the right to try to get in touch with their birth parents.

More painful still, as Andy’s role in bringing the baby into the world had gone unrecorded, he had to accept that his son was unlikely to be able to find him, even if he wanted to.

‘It sounds like a cliche, but not a day went by when I didn’t think about him,’ says Andy.

‘Birthdays and Christmases were particularly painful, wondering what he was like and what he was doing. And whenever I saw a child with ginger hair, I’d wonder, “Could that be my boy?”

‘I had this desperate urge to tell him that if I’d had my way, he would never have been put up for adoption. And that he was loved — and always would be.’

A few months after the adoption, Andy met Hazel, who’s now his wife of 45 years. She had three young children, whom he went on to raise as his own. Andy also has two children from his first marriage — Ian, now 53, and Suzanne, 51 — who lived with their mother, but whom he continued to see regularly.

Between them, Andy and Hazel, 72, now have 12 grandchildren and ten great-grandchildren.

John McNichol with his adoptive mother Eileen

They have also fostered 15 youngsters over the past 15 years, one of whom, 19-year-old Tyler, still lives with them.

Andy says his desire to become a foster parent was partly motivated by the hope that others had been similarly generous and caring towards his son.

‘I was a parent-governor at our local school and a foster parent, making an important difference to lots of other children’s lives. But I couldn’t help thinking: “I should be doing this for my own son.”’

Because, despite having no shortage of people to love, and who loved him, plus a demanding working life running two shops selling gifts and knick-knacks, without his youngest son in it, Andy’s otherwise happy existence was tinged with an ever-present sadness.

While much has been written about the distress many women suffered after they were forced to give up their babies in the decades before it was socially acceptable to have a child out of wedlock, Andy’s experience shows that men can be profoundly affected, too.

‘Andy cried so many tears for his lost son over the years,’ says Hazel. ‘It was always late at night, once we were in bed. His thoughts would turn to John and he’d sob in my arms.

‘It was very upsetting for me to see him so sad, but, given the circumstances, I didn’t think there was anything I could do to ease his pain.’

A few years ago, Hazel put out an appeal on Facebook for anyone who might have information on the whereabouts of Andy’s adopted son, asking people to share her post. Sadly, she drew a blank.

Then, two years ago, after watching an episode of Long Lost Family on ITV, in which relatives are reunited, Hazel decided to stay up after Andy had gone to bed and fill out an online application form, hoping that the producers might find a way to trace her husband’s son.

A few months after the adoption, Andy met Hazel who is now his wife of 45 years. The couple are pictured together in 1974

A year passed before a researcher got in touch, by which time they had lost hope of a happy ending.

Then, last October, a crew arranged to interview them at home and presenter Davina McCall broke the news to Andy that they had found his son, still named John, now living and working as a firefighter in New South Wales, Australia.

Using the details from John’s birth certificate, the programme’s team managed to locate his adoption certificate. While a search of the electoral roll did not find John, they were able to track down his adopted father, who told them he’d moved to Australia and put them in contact.

With tears in his eyes and lips quivering, Andy asked, tentatively: ‘Does he want to see me?’

There were more tears, this time of joy and relief, when Andy learned that John did indeed want to meet his biological father.

The main reason he had not attempted to find his birth parents was fear of being rejected for a second time.

So, a week later, the show’s producers arranged for Andy and John — who had flown in from Australia — to meet in a bar in Somerset, close to where John was born.

A few years ago, Hazel put out an appeal on Facebook for anyone who might have information on the whereabouts of Andy’s adopted son, asking people to share her post

‘I was literally shaking with fear beforehand,’ says Andy. ‘The image, from nearly 47 years earlier, of me standing, desperate to hug my son, but being forbidden from doing so, was imprinted on my memory.

‘Finally, I was getting that chance to put my arms around him.’

John, who was raised by loving adoptive parents in Weston-super-Mare, Somerset, together with an adopted sister, emigrated to Australia in March 2013 to be with his wife Claudia, whom he’d met while she was holidaying in the UK, and his stepdaughter.

John had always known that he was adopted and had been shown a letter by his adoptive parents, written by a social services official, which claimed that his biological mother and father had both been happy to give him up.

Andy, who is now 74, was forbidden by the family of his baby’s mother to get close enough to see his face

Having lived his life believing that he was simply not wanted, he had never attempted to look for them. He was, however, deeply moved to discover that his biological father had been searching for him.

‘I had a great life with my adoptive parents,’ says John. ‘But I couldn’t help wondering what had been wrong with me for my mother and father to give me up at birth.

‘Illogical though it may sound, I’d think: “Did I have the wrong colour hair or eyes? Was I too short or too tall or too fat? Was it because my left foot is bigger than my right?” I wouldn’t say it made me sad, because I’d never known anything different, but getting a call from a TV show early one morning and discovering that my father really had wanted me after all, and still did, was just wonderful.

‘When we finally met, he put his arms around me and said: “I’ve been wanting to do that for 47 years.” I’ll never forget that moment. It felt so good.’

Although John clearly inherited his colouring and looks from his mother’s side of the family, Andy’s and John’s wives were both struck by the similarities in their stocky build — right down to their muscular forearms — and their gait.

John, understandably, wanted to know about Brenda, too.

The news was broken to him by a psychologist employed by the television show that she had sadly died in a car accident more than 40 years earlier. John has, however, since made contact with relatives on his biological mother’s side.

And John hit it off so well with Andy and Hazel that he and his family flew to Britain and stayed with the couple for a fortnight in February.

As both John and Claudia are trained chefs, they enjoyed cooking delicious meals for their newfound — and enormous — extended family.

Andy and John made up for lost time, staying up late, telling one another about their lives over drams of Scotch whisky — a shared favourite tipple.

Hazel decided to stay up after Andy had gone to bed and fill out an online application form for ITV's Long Lost Families

‘It was a shock discovering that my birth mother had died,’ says John. ‘I couldn’t have wished for a better adoptive mother than mine. Another reason I never looked for my biological parents was that I didn’t want to upset her — but she, too, sadly died several years ago.’

Though Eileen, his adoptive mother, died, his father is still alive and happy for John to have been reunited with Andy.

According to Hazel, Andy is a changed man since having John in his life.

Although being on opposite sides of the world means they can’t spend much time together, and Andy, who’s suffered three heart attacks, isn’t up to the 21-hour flight, John plans to make an annual trip to see him.

John also calls Andy every week and the two men chat for up to an hour, updating one another on what’s happening in their lives.

Andy, whose older children were aware of John’s existence and are also enjoying getting to know him, is planning to alter his will so that his youngest son inherits an equal share of his estate after his death.

Well aware that they’d still be strangers without Hazel’s initiative, John has sent her a thank-you card, which she treasures.

‘Seeing Andy so happy at last is the greatest reward I could wish for,’ says Hazel. ‘Chatting to John always puts a smile on his face, and John and his family will always be welcome in our home.’

Andy agrees that finally getting to know his youngest son, and seeing him welcomed into the bosom of their blended family, has made an ageing man very happy.

‘Always knowing that I had a child out there somewhere, a part of me and yet someone I was unlikely ever to get the chance to love, was like a terrible form of torture,’ says Andy.

‘I hope that we’ll have many more years left to make up for lost time.

‘But, whatever happens now, I know I can die a happy man.’

Long Lost Family is on Wednesdays at 9pm on ITV.