Kathryn began researching online and found videos of transgender children in America, like Jazz Jennings, the teenage YouTube personality who transitioned to female aged five. ‘It was all very familiar,’ she says.

Susie Green, chair of Mermaids UK, a charity that supports transgender children and teens, explains that gender is something you come to terms with between the ages of three and five. ‘Gender dysphoria applies to someone like Rudy who is unhappy with their biological sex and wishes to belong to the other one. It’s a medical issue – it’s not about sexuality or even mental health.’

  Photo: Anna Huix

Although Rudy’s GP called it a ‘phase’, Kathryn was determined to be referred to an NHS gender identity clinic. ‘I was frightened of influencing Rudy and initially I didn’t want him exposed to the idea that he could transition.

But by this point, aged four and a half, he’d stopped saying he wished he was a girl, and was now saying that he was one. I’d read that children with gender dysphoria had a “consistent, persistent and insistent” sense of being the other gender, and Rudy definitely ticked this box.’

The clinic advised that Rudy should start to make his own choices and, specifically, recommended that he was allowed to pick an item of clothing. ‘He chose a Disney princess nightie and skipped around the house in it, laughing,’ recalls Kathryn. ‘In the meantime, I talked to my friends: I wanted to prepare a support network. But I still hoped he’d grow out of it because I was frightened of what lay ahead for him.’

Barbara Hutchings* knows exactly how difficult it can be for a transgender teen. Her son Tom, 17, is female-to-male transgender. ‘Tom felt different from an early age but it came to prominence at puberty. When he told us, we were shocked but we accepted it quickly. His thought processes were very mature and he’d been repressing his true gender for years.’

Green explains that if children come out as teenagers, like Tom, it’s because existing feelings come to the fore. ‘There’s an added sense of urgency: they don’t want to become an adult with a gender they don’t identify as. And as puberty progresses, the harder it is to “go back”: body and face shapes alter, Adam’s apples and breasts appear – these changes make it more likely that transgender adults are stigmatised.’

Hormone blockers are a low risk, reversible treatment that stop puberty and allow a child space to consider their options. But in this country, NHS waiting times to get them are long, leading many parents to get help privately either in the UK, which costs hundreds of pounds, or abroad, which costs thousands.

Cross-sex hormones, either testosterone or oestrogen, which start the process of changing the body into one that is more male or female, can only be used once a child is 16. Surgery is only possible after 18, and when the person has lived as their preferred gender full-time for at least a year.

Green is campaigning for a review of legislation for transgender people and wants to see an improvement in support and therapy services for vulnerable teens. UK law contains no provisions for trans people under the age of 18 to gain legal recognition, and options for gender treatment are vastly limited until people are over 16.

‘In puberty, every day feels like a lifetime when unwanted changes are happening. That’s why the UK rates of suicide and self-harm are so high among transgender teens, compared to countries like the US and Germany.’ The Equalities and Human Rights Commission did a survey of 10,000 people in 2012 that found that 1 in 100 people has issues with their gender, whether they have done anything about it or not.

And a study last year by mental health organisation PACE revealed that nearly half of the 2,000 transgender young people polled in the UK had attempted suicide, and that 59 per cent had self-harmed, compared to nine per cent of all of that age group. Meanwhile, one clinic has reported that referrals are increasing by 50 per cent every year.

‘There’s an outdated view that children can’t “know” if they are transgender,’ says Green. ‘Yes, there might be one in 1,000 who changes their mind, but what about the other 999?’

  Photo: Anna Huix

By the time Tom got to the gender identity clinic at 15, he was suicidal. ‘He needed hormone blockers desperately, but was refused them, so we sought care, counselling and cross-sex hormones outside the UK,’ says Barbara. ‘Very quickly he was – and is – so much happier. We’re lucky we could help him but for those who can’t afford it, it’s a desperate situation.’

Kathryn’s experiences have been more positive. ‘I couldn’t fault our NHS care – but then hormone treatments are a long way off for us.’ Towards the end of Year 1 at school, Rudy started wearing girls’ clothes at home. ‘I showed pictures to his teacher,’ Kathryn says. ‘I wanted the school to know what might be coming, and they were really understanding’. That summer, on holiday in Spain, Kathryn and Mark decided to let the then six-year-old Rudy wear what he wanted.

‘Of course, he chose to dress as a girl. I watched him at the disco, chatting to girls, wearing a pink glittery dress. That was a turning point. “This is actually happening,” I thought, and it was a really emotional mix of happiness that he was so happy, and worry about what lay ahead.’

Back home, Rudy chose a girl’s school uniform for the new term and asked to be called Ruby.

‘That worked – we called him Ru anyway,’ explains Kathryn. ‘At school, he told the class he was now a girl. I knew the kids would be telling their parents so I sent an email around, explaining, with links to articles I thought might help. Everyone was brilliant, including the children.’

‘Rudy was now Ruby and he – now she – was so happy. Although that was what I wanted, part of me went through a kind of mourning for the child I thought I had. But that passes.

Sadly, some close family members have struggled to understand and accept our approach, but our friends have been wonderful. And if we ever ask Ruby if she might ever want to be a boy again, she just says, “No way!” There’s never been any doubt in her mind that she is a girl.’

Tom’s school, on the other hand, struggled with his transition.

‘Some schools are great,’ says Green. ‘But some aren’t, and what we need from the Government is blanket guidance in line with the Equality Act.’ Tom left that school and had private tuition for a while, and is now at a sixth form elsewhere.

‘I was in a very sad place for some years, but there’s hope – if you can get help quickly,’ he says. ‘I’m now growing up just like any other teenage boy, thanks to my mum and dad’s acceptance, and being permitted to medically transition.’

Medical transition for Ruby will only start at puberty and in the meantime she’s seen regularly by the clinic as she grows up. ‘I worry about bullying, which is common for transgender children,’ says Kathryn. ‘However, we haven’t experienced it yet, and the good thing is that people are becoming more aware. If all this had happened just five years ago, it would have been much more difficult.’