As Kate Craig-Wood bends to grab something from the office photocopier, she waves one wedge-heeled foot in the air. It's a feminine gesture that matches her expressive way of talking while waving her arms about so that her bracelet jangles. If I didn't know that four years ago she was Robert, a married man, I would never have guessed."It's funny," she says, "I didn't have to try to behave in a more feminine way after I transitioned. It was like suddenly taking the brakes off. I could speak and move in a way that felt natural."Her voice is no deeper than that of the other few women at Memset, the IT company Craig-Wood started with her brother, Nick, seven years ago -- and for which Management Today magazine has just named her one of the 35 most important businesswomen under the age of 35. Her clothes, if anything, are more feminine because "the novelty still hasn't worn off".But there are, she admits, still a couple of clues to her former gender. Her hands are large for a woman of 5ft 8in, and her size eight feet are a little broad. But these are tiny points. Visually, she appears such a normal woman that no one would nudge their companion and titter, as they might when confronted by a 6ft 3in vision with five o'clock stubble. "I'm lucky, I know," she says. "Many people don't dare transition because they know they would never pass for a woman."She could easily get away with "going stealth", as it is called in the transgender community, and blending in with the crowd. "I know married transwomen who haven't even told their husbands about their gender transformation," she says. "They say they have had a hysterectomy."Kate, 32, is open about her history in order to provide the role model that she never had as a confused teenager. "When I was growing up, there was no one I could relate to. Since I started speaking out, I have received hundreds of emails thanking me. Many parents are taking second jobs and remortgaging their homes because they are desperate to help children who say they will kill themselves if they have to go through puberty in the wrong gender."Kate is comfortable with herself. As "Robert", she was so consumed by self-loathing that, one day, she got into her car, left the seat belt off and drove at 100mph, hoping to hit a tree. Nor is she critical of the attitudes she encounters among "normal" (her word) men and women. Kate -- who has an MA in Biomedical Science -- says that understanding has developed so rapidly that it is hard for society to keep up."Gender is not binary, but a mosaic. Nor should it be confused with sexuality: sexuality is about who you fancy; gender is about who you are. It's innate. You can't change it."Many doctors still say that gender dysphoria is about being gay, but not being able to deal with it. For some it may be. But for me it wasn't. I didn't become a woman in order to have sex with men. There are chromosomal reasons why some people have a male brain in a female body, or vice versa. It may also have something to do with the womb being flooded with hormones during pregnancy."According to the British National Health Service (NHS), 20 in every 100,000 people have a gender identity that "conflicts with their visible sex characteristics" -- 80 per cent of whom are men who feel like women. Numbers are doubling every five years and 6,000 people in the UK have undergone "corrective" surgery."It is more socially acceptable for women to behave like men: the stereotypical butch lesbian. Women who take male hormones become passably male. Transwomen are more visible."From early childhood, Kate knew she was really a girl."I hated football and wanted to spend time in my tree-house, which was clean and tidy and had a stove. I was so ashamed that I couldn't talk about it and became introverted. It was worse as I hit puberty. I envied my sister developing breasts while I was becoming a man. I tried dressing up in her clothes, but when I looked in the mirror I saw a boy's face. It was horrible."But there was an advantage to growing up as a boy. Her father, a technology entrepreneur, talked business to her and she was expected to be good at "boys' subjects", like maths. Early on, she knew she wanted to be a businesswoman, though she only achieved the latter part at 29, after nine years of marriage."I loved my wife deeply, but I feel terribly guilty at the pain I caused her," she says.She thought she could control her desire to be a woman by siphoning it into playing computer games as "Kate". The reverse was true. She became increasingly tortured. "When my wife said she wanted to have children, I knew I had to do something."After the night when she tried to wrap herself around a tree, she knew the only alternatives were "kill or cure". The NHS could not help her."I was told that I had to spend a year living as a woman with no treatment, not even laser hair removal, so I started taking hormones and became androgenous. Then, in 2005, when facial feminising surgery became available, I decided on gender correction. It's immensely traumatic, complex and risky. No sane person would do it unless they knew their body was wrong."Changing her face and body cost her Â£50,000. Sadly, her father died before she became the person she'd always believed herself to be, but her mother and siblings coped with the change. Still, she had a difficult time learning about being a woman."I found myself in abusive relationships with men," she says; now she has fallen in love with a woman she is much happier, though she is still attracted to men. It amuses her to observe how she has become better at multitasking, and communicating. Her only sadness is that she cannot have children.She has two more wishes: for more women to join her in IT; and for more children to be helped at an early stage over issues of gender. Through the charity Mermaid, she campaigns for those who feel they are in the wrong body to be given hormone blockers to delay puberty until they are 16.Alongside the awards in her office, I notice driving manuals. Now she is hormonally a woman, does she have trouble parking "No," she laughs, "but I have never been any good at map reading."