When I rang the doorbell of Labour’s candidate for Sutton and Cheam, I thought I had a fairly clear picture of the woman I was about to meet. Anyone who stands for a party that polled 9% in the seat last time round has to be pretty bold. To do so as a blind woman with impaired hearing must take serious nerve. To have won the nomination without mentioning her transgender identity, then to announce it 12 months later without even warning her own party leader, suggests a degree of audacity uncommon even by the standards of politicians.

Within days of her decision in December to out herself as Labour’s first transgender candidate, Emily Brothers was ridiculed by the Sun’s Rod Liddle, who wrote: “Being blind, how did she know she was the wrong sex?” By the time we meet a week later, Brothers has seen off his mockery with a crisp retort (“I wonder how he knows he’s a man when he turns the light out”), and extracted a rare public apology from the columnist, if not the tabloid.

“If anyone thinks I’m just going to go quietly into the corner, they are sorely mistaken,” she says coolly, dismissing Liddle as “a ridiculous man writing in a rag of a paper”.

Brothers’ manner is rather stiff and combative at first. She has been “impatient with the world” since her teens. “I don’t do rules very well,” she says, adding: “If people tell me I can’t do something, it’s like a red rag to a bull.” She can see no legitimate grounds for local party members who selected her to feel in any way deceived: “I don’t think I said anything during the selection hustings that was inauthentic.”

But by the time I leave, invulnerable is the last word I would use to describe Brothers. Like many people who have lived with a secret for most of their life, she is not very skilled at telling her own story, and the narrative that unfolds is by turn halting and digressive. But once she has started, she doesn’t want to stop. She talks for more than three hours, weeps several times, and once or twice I’m almost moved to tears myself.

Brothers has never known what she looks like. Born on Merseyside in 1964, the middle child of working-class parents who lived in a “very basic flat, two rooms, inner-city”, she was diagnosed with aniridia – a condition affecting the iris – at six months old, and spent the first 10 years of her life undergoing eye surgery, sometimes weekly, in a futile battle to save what little sight she had. At seven she became a weekly boarder at a Catholic school for blind and partially sighted children, and “began to feel more and more apart from my family, because my world was so different to theirs”. But she felt isolated within the school, too, unable to believe in God, increasingly insomniac and severely depressed by the time she reached her teens. “I didn’t even have the words to express it. I knew I had male characteristics, but all the time I just imagined myself as a girl.” She “acquired” a skirt and a top, and would wear them in secret, but was “terrified” of being caught.

Getting into higher education was a battle – “In those days blind people went to rehabilitation centres. They did basket weaving, or piano tuning; the clever ones did physiotherapy” – but at Teesside university she became involved in student politics and “started to get the hang of socialising”. For the first time in her life, she learned of the existence of “cross-dressers, ladyboys in Thailand, that sort of thing. But that all sounded too sexualised, that wasn’t me.” With no access to magazines or newspapers or public libraries, she still had no name for how she felt, and though she had several girlfriends, she didn’t dare tell them about it.

Working at an organisation for blind people in the late 80s, she fell in love with a colleague who was also blind, and in 1993 they married. “But I had serious doubts. Not about how I felt about her, but I did question whether it was the right thing for me to do, because I had this secret.” The couple had a son, then a daughter. When Brothers’ wife found a skirt hidden under their bed, she thought her husband was having an affair.

It wasn’t until the internet arrived in the late 90s that Brothers began to read about gender identity, and finally understood her condition. She began attending meetings of the Beaumont Society, a transgender support group, found her way to a psychiatrist who specialised in transgender identity, and in the summer of 2006 summoned the courage to tell her wife. “She was shocked, but not surprised. She said it was like somebody suddenly switched on the lights. But it was very difficult. I got more depressed. I wanted us to stay together, but she didn’t want to be married to another woman, and I knew I wanted to live full time as Emily.”

But Brothers wasn’t sure she ever could. She didn’t know what she looked like, so didn’t know if she could ever look like a woman. “I thought: don’t be ridiculous, no one will ever think you’re a woman, you can’t pass as a woman. I didn’t want to become some sort of point of ridicule for people to poke fun at. And I’d heard so many stories about people being harassed in the street. I thought: I don’t want to be a spectacle, and I don’t want to be a glamour model, I just want to live as an ordinary woman. And I didn’t understand that I could do that.”

Emily Brothers with Labour leader Ed Miliband at last year’s party conference in Manchester

She was depressed and frightened. She began spending a lot of time alone at the family’s holiday home on the Isle of Wight. “And one night in December 2006 I was walking home along the sea front in the early hours of the morning, wearing men’s clothes. There was nobody around, and I walked down to the beach and walked into the sea.” She begins to cry. “If it had been a rough sea that night, a rough tide … I don’t think I had the physical strength to have fought it. I was fully dressed in the sea, up to my neck, but I didn’t quite have the courage to let go. And I stood there for ages. It was freezing, but I didn’t feel cold. And then something brought me back. I think it was probably my children. Thinking of my children.” She breaks off, weeping.

“And I remember thinking that it was just a shambles, but if I couldn’t take my own life, I had to face up to it. I went back up the cliff top, back to the house. And it was sort of – I can’t live like this. I was upset, I was angry, I hated it. I took the clothes off – I hated them. It’s a symbol of something I don’t want to be. This isn’t me. I threw them in the bin. I just threw the clothes away. And after that, I was increasingly living as Emily.”

After six months of rows, the couple told their children, then 12 and 10, and Brothers moved out of their south London home. “That was probably the worst day of my life, the day I left,” she chokes, breaking down in tears again. “I’d heard so much about other people losing contact with their children. I thought I might lose them. And of course, they were shell shocked. They said: ‘We still love you, but we don’t understand.’” Brothers moved to the Isle of Wight, underwent hormone and voice therapy, and began to live openly as Emily. “And when I went out, for a coffee, or shopping, I wasn’t being hassled. And I began to think: I might really be able to do this. This might be possible.”

The vulnerability of not knowing what she looked liked is manifest in her relief and understated pride as she recalls the reassurance of others’ reactions. After she visited her wife a few months after moving out, she left in a local minicab and recognised the driver’s voice at once. “But when we started talking, he said: ‘Oh it’s a shame about Mrs Brothers. Her husband left her, you know. Apparently he was a terrible womaniser.’” When she moved back to London and returned to her job at the Equality and Human Rights Commission, another taxi driver told her: “I used to pick up a blind guy from your office, and he was a right miserable so-and-so. But you’re very chatty, love.” In 2008 she travelled to Thailand for genital surgery, and completed her transition. “I contemplated breast surgery, but fortunately I didn’t need it.” She touches her bust. “This is all me. Hormones did the job. Which is very, very unusual, and might suggest some kind of intersex.”

Following the divorce, Brothers moved back into the former marital home, where she now lives with her 20-year-old son. “Six months ago,” she says, beginning to cry again, “my son said: ‘I miss my dad. But if you were to go through a gender reversal now – well, I don’t want to lose Emily.’” If her old neighbours have recognised her, none has ever said anything to her. She outed herself last month, only out of fear that if she didn’t, a newspaper might discover her secret and do it for her.

Not once has anyone questioned her gender. In fact, the very first person ever to laugh at her was Liddle in the Sun. It hurt, she says, only because of what her parents must have thought.

“I’m sure they’ll be aware of all the publicity about Rod Liddle. His joke probably just confirmed their worst suspicions about what the world thinks, and they’ll assume this is what I’ve been going through for years, people ridiculing me. Because they’ve never met Emily. They’ve never tried to get to know me.”

When Brothers’ marriage was ending, she travelled north to tell her parents why. “But I knew my family was never going to accept me. They said it was a midlife crisis, they said: ‘You need to go to the doctors and get a pill.’ Then they got very angry after I left, and we’d talk on the phone, and they said: ‘You’re sick in the head, you’re going to be toddling around the streets and people are going to be laughing at you. How could you do this to us? Are you satisfied now?’ They were very aggressive.” Eventually she wrote to them to say: “Until you can respect me and give me some dignity, then contact can only be by correspondence.” She hasn’t seen or spoken to them since.

In 2013, 10 days before Christmas, Brothers received a letter from her parents telling her that her younger brother had died a month earlier. “It said: ‘We didn’t invite you to the funeral because we can’t have someone like you there.’” Her voice falters. “That’s how deep it goes. I wrote back to them and said: ‘I know this is such a difficult time, but it was wrong to exclude me. I enclosed some Harvester vouchers and said please, go out and have a meal.’ I got a letter back saying: ‘You don’t know what it’s like, we’ve now lost two sons, and we’re sending the vouchers back because if we eat your food we’ll choke on it.’”

• This article was amended on 3 January 2015 to correct the spelling of Isle of Wight. It was further amended on 5 January 2015. An earlier version said both Rod Liddle and the Sun had apologised to Brothers. That is true only of Liddle.

