As a British Army Captain, she was one of just three women at her base outside Basrah in Iraq, fighting alongside and serving as third-in-command of hundreds of male soldiers.

After immigrating to Australia to work in microbiology research, she became the first woman to referee Premier rugby in Queensland.

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And last week, Dr Horton became the first female principal of The Armidale School, after winning an international search for a new boss in December 2020.

"I've been the first woman at a few things and there's a part of that that loves that. I wish it wasn't particularly noteworthy that I was the first," she said.

The choice follows a decision in 2015 to become the first co-educational school in the prestigious Great Public Schools network, after 123 years of all-boys' education. Dr Horton said her selection was not related to that choice, and that she was selected on merit.

It was a "straightforward choice to appoint a women, but I think it was also a courageous choice. TAS was one of the first schools to break that mould," she said.

"As a women, there's an awful lot of things you come up on over the years and say - how have we not got this? All we can do is be positive as we push against it."

It's just the latest glass ceiling in a career of smashed precedents for the British-born former academic.

From the 'blokey' culture of Rugby Union to the even more macho culture of her home country's army at war, she's repeatedly been the first woman in her position.

In 2003 and 2004, then-Captain Horton spent six months serving as a Squadron Operations Officer of a unit of combat engineers outside Basrah.

She hadn't even met the 135 men in her squadron of British Engineers she would help lead under extreme conditions before she got off the plane. There were three women in the camp - the others were a chef and a signaler.

Under the circumstances, she felt like she needed to work harder than a male officer would have - but in retrospect now has a different perspective.

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"I was actually quite young then, in my mid-20s. That's pretty young to be in that position. I almost feel like it was a different me. I feel quite proud of myself that I managed to do that. It is a fairly scary and surreal experience," she said.

"It did change my world view. It taught me to understand or consider situations from different point of view."

After getting her post doctorate in Canada, she worked to study HIV among Kenyan sex workers on a Gates Foundation Grant.

She later immigrated to Australia and worked in microbiology research at Griffith University.

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Most recently she worked as a chemistry and physics teacher at Anglican Church Grammar School in Brisbane.

Head of school, Alan Jones, will serve alongside Dr Horton until the end of term three to ease her into the position, before retiring.

Dr Horton said she had "millions of ideas" for the school, but her intention, given a mid-year start, was to spend six months listening to people before implementing any of them.

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