Caitlyn Jenner has always felt "very different" in her "soul"

She said: "Caitlyn has always been in there since I was [small].

"Growing up in the fifties and sixties, there was not even a word about gender identity or being trans. So I had no idea why in my soul I felt very different than most people. And then I found sports in fifth grade. It was a running race and I wound up having the fastest time in the whole school. I said, "This is cool, I just beat everyone else!"'

And the former decathlete - who won gold at the Pan American Games in 1975 and the Montreal Olympics the following year - credits "little Caitlyn" inside her for driving her to sporting success as she doesn't think she'd have been so obsessive if she was just an "average" boy.

Speaking on Irish TV programme 'The Late, Late Show', she said: "But I wasn't average I had all these things going on in my soul. I tried to not just be on my high school team, I tried to be the best in the world at something. I think I was more obsessed, I was more determined, I worked harder than the next guy.

"And to be honest with you, I really thank little Caitlyn for living in there, because it made me out-train them. It made me out-work them because I had more to prove than the next guy."

But Caitlyn feared she'd pushed herself too far when she scooped her double gold.

She recalled thinking: "'Oh no, what did I just do? Did I build up this character Bruce so big that I'm stuck with him for the rest of my life?' And I thought, 'What am I going to do?' "