Kellie, then known as Frank, retired from boxing in 2013 saying at the time she had "fallen out of love" with the sport. She has now said she wanted to retreat from the public eye and undergo gender reassignment in private.
"I thought that what I wanted to do was to transition in a positive and private way. I closed my websites down, took my Facebook down and my Twitter account so that I could transition peacefully," she told The Mirror.
Earlier this month, she publicly revealed she had been living as a woman for the past year, saying: "I was born in the wrong body and I have always known I was a woman."
In the past two years, 61-year-old Kellie - who has three children - says she has undergone hormone therapy, hair removal, voice coaching and many hours of counselling.
Kellie's had massive support from the public, former colleagues and the world of sport since making her announcement.
"It just goes to show you how the world is changing for the better," she said. "Many other people in my position have been severely traumatised for years from what they've been through. I cannot thank the British public enough for their care and understanding."
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