IT'S a well-worn phrase that 'life begins at 40'.

But for Katie Cornhill, a station manager at Hampshire Fire and Rescue Service, the expression has more than a grain of truth in it – because it is only since reaching that milestone birthday that she has openly been living as her true self: a woman.

Katie was born in a male body and knew as young as four that there was a mismatch between the way she felt and the way she looked.

Throughout her childhood she experimented with wearing girls' clothes in private but at the age of nine her family discouraged her from doing this, and she began to bury her feelings.

She excelled at traditionally male pursuits, including joining the Royal Marines, passing out as a section commander and going on to serve for six years, including a stint in northern Iraq and southern Turkey. It was a life she loved.

But at the same time, she was keeping her female identity hidden. Katie met her ex-wife shortly before joining the Marines, and told her about her gender identity.

Her wife supported her, as she told the Daily Echo in an exclusive story, shortly after she transitioned, in 2012.

"Sometimes I would sit in the front room as a woman with her, reading magazines and doing our nails together," she said.

“We were ok managing my gender identity, identifying as a man to the outside world, knowing I couldn’t really live as a woman to the world because it would have jeopardised our relationship, my career, everything.

“The question rose early in our relationship of whether I wanted to live as a woman full time but the answer was ‘no’."

The couple went on to have two daughters, now aged 18 and 14.

After several years, they separated, for reasons Katie says were unconnected to her gender identity.

After the separation, Katie began to feel more and more that occasionally visibly identifying as a woman in private was not good enough.

“I realised you are who you are inside. There’s nothing you can do about that and I shouldn’t be afraid of being who I am inside.”

Katie began living full time as a woman in March 2012.

Now, five years since she first opened up in the Daily Echo about her transgender history, she reflects on where her journey has taken her and what the future might hold.

She made the decision at the outset to be open about her transgender history in public.

"I've had to live times in my life very privately, without bringing my full self into a conversation, or a relationship," she says.

"It's energy sapping. You have to pretend and check your conversations and that's the wrong thing to do.

"I made a concrete decision right at the beginning to be open about the fact that I'm a woman with a transgender history because, fundamentally, I was conceived who I am and I should never have had to hide.

"I know that there are millions of other people in the UK who feel in some way the same, and I wanted to take them with me and share my journey with them.

"I know that it's different for different people, but for me, from the moment I knew that I wanted to be able to live in my true gender identity, I wanted to take other people with me, and you can't do that by not being open about yourself.

"If you have the strength of character, I think there's a real need to be visible. It's important for other people to see that there are people who are different, and also to be a role model for those who feel they are in any way different, and to show that's it's OK.

"I'm happy to be known as Katie, a lesbian and a woman who has a trans history."

Since first speaking to the Daily Echo, Katie has medically and surgically transitioned, regularly taking hormones and having her gender confirmation surgery around two years ago.

"I feel very aligned now," she says.

"It's been a very validating process, to finally be able to look in the mirror and see myself the way I should be.

"Previously, I'd very often look in the mirror and feel a sense of depression that I wasn't who I should be and that I had to keep hiding myself away.

"Throughout my life, the energy I exerted doing that, psychologically, physically and emotionally, must have been immense.

"I could probably have lit up New York if you could have captured it all!"

Katie says that reactions to her transition have varied, from those who have struggled with her journey and with whom she is no longer in contact, to those who have not only accepted it but also embraced it.

"Very early in me going through my transition at work, an older guy had something on his computer that he was laughing at. He called people to see it so I went to look too.

"It was a photo of a so-called 'ladyboy' who was naked. I walked away and thought 'how do I deal with that?'.

"It was disrespectful. I wanted to educate him, so I identified why it was wrong and also suggested that he messaged the person who had sent it to him and said he didn't want those emails sent to his workplace.

"I didn't feel upset or angry. To me, those emotions can be quite destructive.

"I feel that there's an opportunity to think about what you can do about the situation to make it better for someone else in the future, and engage with people."

Katy says she feels that it is always important to engage with anyone who is oppressing others, whether it's challenging students who are joking about other people on a train, or so-called trans-exclusionary revolutionary feminists, a very small sub group of feminists who deny the identity of transgender women.

"When I see these things in the news, I don't think 'you're being oppressive to trans people'. I'm acutely aware that that's their route of oppression, but what I see is a person being oppressive to another human being.

"When people are hostile to the transgender community, there can be a tendency to react in very negative ways, and that doesn't help the situation.

"I feel we need to use it as an opportunity to address the thoughts and feelings that are behind the prejudice, and break down barriers.

"People don't transition to take anything away from someone who was fortunate enough to be born a genetic female."

Katie spends much of her time educating others about equality and inclusion and working towards achieving it, particularly within the fire and rescue service.

Two years ago, she founded Quiltbag, the fire and rescue services lesbian, gay, bisexual, transgender and intersex (LGBT+) staff support network.

She is also an advocate of LGBT+ lobbying and campaign group Stonewall, a mentor for the Princes' Trust and has often spoken publicly and to the media about transgender and other diversity and equality issues.

At some point, she anticipates stepping back from her role as an equality champion, but it doesn't look likely to happen anytime soon.

"I'm not going to be putting my history and experience into what I do forever," she says.

"There will come a time when I blend into the background, but for now, I've got stacks of energy for this."

For Katie, the only things missing in her life are a partner and better relationships with her daughters.

She is in regular contact with her eldest daughter, who is 18, but has no relationship with her 14-year-old.

"I wish, of course, that I was very much an integral part of both my daughters' lives," she says.

"It saddens me immensely that I'm not, especially around Christmas and birthdays. I'm always hopeful that I will be much more a part of their lives in the future, but I can't force this to happen.

"It would only serve to make worse the distance that was created by the individuals, institutions and organisations that acted to remove me, or omitted to prevent this from happening, when they were younger, for no reason other than that my gender identity was outside the traditional norms of male and female.

"It makes me cry when I think of the time together that we have lost, that can't be looked back on, because they never happened.

"It leaves me feeling like a piece of me will never be replaced.

"I was always a very loving and caring parent, and always will be."

* Katie is taking part in the Great South Run on October 22, in aid of the Fire Fighters' Charity. To donate, visit her Just Giving page: justgiving.com/fundraising/katie-cornhill1