Prof Djordjevic fears money is at the root of the problem, and says his reversal patients have told him about making initial enquiries to surgeries and simply being asked to send a cheque in return.

“I have heard stories of people visiting surgeries who only checked if they had the money to pay,” he says. “We have to stop this. As a community, we have to make very strong rules: nobody who wants to make this type of surgery or just make money can be allowed to do so.”

To date, all of his reversals have been transgender women aged over 30 wanting to restore their male genitalia. Over the last two decades, the average age of his patients has more than halved, from 45 years old to 21. While the World Professional Association for Transgender Health guidelines currently state nobody under the age of 18 should undergo surgery, Prof Djordjevic fears this age limit could soon be reduced to include minors.

Were that to happen, he says, he would refuse to abide by the rules. “I’m afraid what will happen five to 10 years later with this person,” he says. “It is more than about surgery; it’s an issue of human rights. I could not accept them as a patient because I’d be afraid what would happen to their brain and mind.”

Referrals to adult and child gender identity clinics in the UK have increased dramatically over the past 10 years. In April, the Tavistock and Portman NHS Foundation Trust, the only clinic for adolescents in England, reported 2,016 referrals to its gender identity development service, a 42 per cent increase compared to the previous year, which in itself marked a 104 per cent increase on the year before that.

The clinic stresses the majority of its young referrals do not end up receiving physical treatment through the service. While NHS guidelines state young people should not be given cross-sex hormone treatment until 16, concerns have been raised about the lack of regulation particularly in the private sector.

Earlier this month, it was revealed a Monmouthshire MP, Dr Helen Webberley, was being investigated by the General Medical Council (GMC), following complaints from two GPs that she had treated children as young as 12 with hormones at her private clinic, which specialises in gender issues.