At 42-years-old, Walt Heyer was, by all accounts, a happily married man with two children.

But it was then he decided to undergo gender reassignment surgery to become a woman - a decision he would later say had a 'tremendous, destructive process' on his life. He reverted back to being a man just eight years later.

Now, at 74, Walt, from Los Angeles, tells MailOnline he should never have been allowed to have the sex change in the first place.

And he claims hundreds of others are making the same mistake because surgeons are not properly evaluating their motives to change gender.

He was delighted at being a female at first, having felt trapped in the wrong body since he was five years old.

But the Californian said the elation soon gave way to much darker feelings: 'Immediately after the procedure, you're in a state of euphoria because you battle it for so long.

'You think this is wonderful and fabulous and you think your life's going to be good and then as time goes on, there's this funny little thing that happens in life. It's called reality.'

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Sex change: Walt is pictured here in 1984, one year after he underwent surgery to become 'Laura Jensen'

Reversal: This is Walt in 2007, following his decision to revert back to being a man - eight years after his initial surgery

Walt's genitals were removed as part of the transformation. He also received breast implants, treatment to reduce the hair on his face, and a course of estrogen hormones for as long as he remained a woman.

While dealing with the difficult physical transition, which he describes as a 'battle', he also faced cruel discrimination in his professional life.

He said: 'I ended up for a long time unemployed and trying to figure out what to do.

'I went to over 200 interviews before I got a job, because people don't really want a transgender person – they don't want to hire them, so it took a long time.'

In the mid-1980s, Walt says he came to the realisation that his desire to change genders came from deep-rooted childhood trauma - rather than a genetic disorder. But with no safe reversal procedures at the time, it was already too late.

It is accepted that people like Walt, who believe they were born inside the wrong body, suffer from Gender Dysphoria.

The condition was once believed to be psychiatric, but is now recognised as a medical condition by bodies such as the NHS. Recent studies suggest that it is a biological disorder caused by hormonal imbalances before a baby is born. The NHS does not class it as a mental illness.

Walt, however, claims that his gender confusion was caused simply by his environment and family relationships.

It is a controversial viewpoint, and one that will upset many. But the 74-year-old is adamant that he should never been allowed to go through with the procedure. Experts have told MailOnline that the procedures in Britain are robust - and that gender dysphoria must be diagnosed by at least two specialists before procedures are carried out.

But Walt now says: 'Gender dysphoria is a psychological condition where you are dissatisfied with your gender.

Most provocatively, he adds: 'Nobody's ever born a transgender. They're manufactured as a result of something, a developmental childhood issue that has yet to be determined for many people.

'In retrospect, I can see that changing genders, quite frankly is just pure foolishness.'

Happy life: Walt was a happily married man at 42, and with two children, when he decided to undergo a sex change

Elation: He told MailOnline: 'Immediately after the procedure, you're in a state of euphoria because you battle it for so long'

Growing up in Los Angeles, Walt had a tough but bearable start in life with a strict mother, a part-time policeman father - living in the shadow of a 'brainiac' brother.

When he was five, everything changed.

'It was then my grandmother, when I was being babysat by her, started dressing me in female clothing. She even made me a purple chiffon evening dress,' he said.

'And when dad found out what grandma had been doing, and dressing me up like a girl, it did change everything.

'My daughter was very, very upset. And my son said it would be easier if you were to die, because then at least I could talk to people about what you were going through.' Walt Heyer

'His adopted brother Fred began to sexually molest me. Mom's discipline got even more severe and I would learn much later in life that on one occasion, her discipline was so tough, she thought she had almost killed me.'

The treatment he suffered from those entrusted to protect him made him feel like he was 'a girl trapped in a male's body', he said, and he became reclusive because of it.

37 years later, he would finally take the drastic step to become a woman - and he lived for eight years as Laura Jensen.

He had divorced his wife three months before the surgery because he did not want to put someone else 'through that difficult time'.

The relationship with his ex-wife remained civil but his daughter, 15 at the time, and son, 12, were less understanding.

Walt said: 'My daughter was very, very upset. And my son said it would be easier if you were to die, because then at least I could talk to people about what you were going through.

'When a father does that, you're betraying your children and what came to my mind later on was I saw myself as much more important than my kids.

'That is probably the most self-centred, narcissistic thing a person can do – it's just nonsense to place yourself over a couple of kids, who needed someone to be there for them.'

Psychological issues: Walt (pictured as a child)believes his desire to change genders stemmed from early emotional trauma

Childhood trauma: Among other hardships Walt (centre) suffered, he was sexually abused by his uncle

Evaluation: Walt - pictured here on his wedding day in 1962 - believes patients are not vetted thoroughly enough before sex change surgery

He was optimistic at first, having finally realised the dream he had been nurturing as an escape since childhood.

As Laura Jensen, he eventually landed a well-paying job working for the US government at the Federal Deposit Insurance Corporation.

It wasn't until he began studying psychology at the University of California Santa Cruz that he said he came to the self-realisation that being transgender was a 'psychological disorder' - and he'd made a huge mistake.

'All they do is pump people full of hormones, put in breast implants and declare that they've manufactured a female. It's biologically impossible to make a man into a woman.' Walt Heyer

He said: 'Once I studied psychology, I realised that it is impossible to biologically transform someone from one gender to the other, and that's the moment you realise that it's psychological condition, and not medical.

'All they do is pump people full of hormones, put in breast implants and declare that they've manufactured a female. It's biologically impossible to make a man into a woman.'

After eight years of living as Laura Jensen in San Francisco, he had would receive another operation to revert to his 'birth gender'.

So after eight years, £20,000 and untold damage to his health and relationships, he once again became Walt Heyer.

Now, through his website 'Sex Change Regret', he acts as an unofficial counselor to those considering the same procedure.

And after many emotional discussions, he has finally rekindled his relationships with his children, who now call him 'their hero'.

He said: 'I met with each one of them, and told them how sorry I was that I didn't make them the focus of my life - and I focused on some gender difficulties that I was having.

'This all happened after I realised what a horrible mistake I'd made and so the relationship took its time to heal, but now it's fine.'

Transition: After eight years, £20,000 and untold damage to his health and relationships, 'Laura Jensen' once again became Walt Heyer (pictured)

Returning the favour: Walt (pictured) now runs a website where he acts as an informal counselor to those thinking about getting a sex change

Walt says hundreds of people contact him for advice prior to having a sex change, and on how to deal with their regret afterwards.

He claims that every single one of them can trace their need to change back to a childhood issue, and better psychological evaluation would discover that - saving them both money and heartache.

Walt himself says he suffers from dissociative disorder, which disrupts his memories and sense of self-identity. Mental health charity Mind says dissociative disorders disrupt 'your sense of reality and who you are'.

GENDER DYSPHORIA EXPLAINED Gender dysphoria is a condition where a person experiences discomfort or distress because there is a mismatch between their biological sex and gender identity. Biological sex is assigned at birth, depending on the appearance of the genitals. Gender identity is the gender that a person 'identifies' with or feels themselves to be. While biological sex and gender identity are the same for most people, this is not the case for everyone. For example, some people may have the anatomy of a man, but identify themselves as a woman, while others may not feel they are definitively either male or female. This mismatch between sex and gender identity can lead to distressing and uncomfortable feelings that are called gender dysphoria. Gender dysphoria is a recognised medical condition, for which treatment is sometimes appropriate. It is not a mental illness. The condition is also sometimes known as gender identity disorder (GID), gender incongruence or transgenderism. Some people with gender dysphoria have a strong and persistent desire to live according to their gender identity, rather than their biological sex. These people are sometimes called transsexual or trans people. Some trans people have treatment to make their physical appearance more consistent with their gender identity. Gender dysphoria is not the same as transvestism or cross-dressing and is not related to sexual orientation. People with the condition may identify as straight, gay, lesbian, bisexual or asexual, and this may change with treatment. Source: NHS Choices Advertisement

It can be considered an involuntary defence-mechanism to shield the victim from some kind of psychological trauma.

However, he believes many pre-operative patients need greater help with mental health issues before they take the decision to go ahead. He said: 'There's a huge element of trust that all of the pre-surgical transgender people place in the hands of the clinicians.

'They make them go through counselling, but it's more of what I would frankly refer to as a rubber stamp because they're looking to approve them.

'All of them have some level of depression, and we're not treating them – we're just cutting off body parts and giving them a new name and a new gender.

'Biologically, no one can transport to the other gender, it's not even possible. Because they use a guy's penis and just invert it, the guy hasn't lost it, it's just going the wrong way.'

Walt claimed the regret can be so severe that post-operative patients end up self harming, and even committing suicide.

The Gender Identity Research and Education Society (GIRES) makes it clear that gender dysphoria is a condition that needs to be taken more seriously.

Trustee Terry Reed told MailOnline: 'Studies have been done to show it is not something that’s related to abuse or anything else in childhood.

'Children under school age, for instance, change their gender role and are absolutely adamant about who they are.

'There are many studies that show that biological factors, especially hormonal and genetic, impact on the neurobiology of the brain and are crucially important in the development of gender identities.'

'It would completely wrong to say there is insufficient screening beforehand - you could make an equally plausible argument that there is too much screening beforehand.'

Christella Antoni, gender expert and speech therapist based at the Gender Identity Clinic in west London, said: 'In the health service in Britain, patients' most common complaint is that they are actually made to wait too long.

'There are very stringent procedures in place to make sure people are actually suffering from gender dysphoria and really need the operation.

'In a handful of cases people choose to 'detransition' [reverse the operation] at a later stage, but this is quite rare, and it is more likely to happen when patients have funded their operation privately and perhaps not been honest about how long they have been living as a woman or a man.

'But the procedure before an operation is very strict. You need to have a diagnosis of gender dysphoria, then a second opinion.