The size 10, attractive 43-year-old used to be a rugged, macho, 16-stone paratrooper.

A snapshot of Jan as she was – as Captain Ian Hamilton – shows a tanned, muscular, well-built masculine figure in combat fatigues.

The decorated officer served in Bosnia, Iraq and Afghanistan, but started the process just over a year ago to become a woman after decades of turmoil, convinced that he should have been born a woman.

Jan, who now lives in Lytham, was the first officer and paratrooper in the history of the British Armed Forces to undergo a sex-change operation.

It was not a decision Jan, who tonight tells her incredible story in a Channel 4 Cutting Edge documentary "Sex Change Soldier", took lightly.

"I grew up in a small village in North East Scotland and my daddy was not happy that I liked girlie things. I was sent to boarding-school, one for boys, when I was 10. When there were school productions and female roles, I was always happy to play them. But I ended up being abused.

"My dad was quite violent towards me growing up and I realised that violence and being macho could get you things as a man. "My role models were guys like John Wayne and after watching A Bridge Too Far in which Sean Connery stars as a paratrooper, I remember thinking that if I was like that, I would be a man.

"So I went off and joined the Army, but then I suffered a mental breakdown."

Jan, or Ian she she was then known, started working in the media and took a number of courses, before – at 35 – going back to the Army.

Ian was stationed in Northern Ireland, Iraq and Afghanistan and while in hospital after being caught up in a road-side bomb, caught a serious secondary infection –and was treated in Blackpool.

He was due to take up a post as head of media relations in Gibraltar, but made the tough decision to change gender and informed bosses.

Jan says the Army ordered her to report for a medical, as a male officer, and when she refused, the job offer was withdrawn.

Losing out on the the job was not the biggest loss suffered. "My family disowned me. My mother sent me five suitcases of things to do with me, photos of me and so on. I was told never to have contact with them again. An Army officer told me I had gone from hero to zero in one day.

"I got married in 1995, when I was 31. I loved my wife very much, I still do. But she wanted a man. Sexual relations were very difficult and we ended up in separate rooms. We divorced two years ago. We are still in touch and I hope she finds happiness. I never told her how I felt until I made my decision. I never told anyone.

"I genuinely thought there was something so very wrong with me, that I must be cursed, evil."

It also cost her financially."I had no money, no job.