I was in the closet for three hours once in 1972. It was dark, uncomfortable, and really cramped. Plus, I was convinced I wasn't alone (a crumpled jacket lurking in the corner looked pretty dangerous). I was five and my brother, Andrew, then 10, and my sister, Carole, 13, had shoved me into the coat closet because, well, really for absolutely no good reason. I mean what baby brother has ever annoyed his siblings to the point of needing to be locked up or tied down?
This story still gets a laugh from my nieces and nephews. Depending on who's doing the telling, Uncle John was either locked up for 30 fleeting minutes or for three long, tortuous, oxygen-starved hours. As simple as the story is I think it's an apt metaphor for the way I've chosen to live my life - openly, honestly, with no regrets. And, whenever I can, I try to confront the monsters in the dark. As my favourite Jerry Herman song proclaims: "There's no return and no deposit. One life. So open up your closet."
FIND OUT MORE...
John Barrowman: The Making of Me is one BBC One at 2100 BST on 24 July
Or watch it later on the BBC iPlayer
My sexuality has never been deliberately hidden. I'm in a committed relationship with the love of my life, Scott Gill, and he is as much a part of the family as my sister's husband, Kevin, and my brother's wife, Dot. However, just because I'm comfortable with my sexuality doesn't mean that I'm not curious about it and that's one of the reasons I agreed to take this journey to discover the making of me.
I remember vividly when I first realised I was gay. I was nine and a few of my friends were looking at some mild porn in the playground during recess. While they were ogling the well-endowed female models, I couldn't take my eyes off the male members in the shot.
Growing up in the Barrowman household, conversations about sexuality were never taboo. Over the years, we've talked about many of the theories that may explain what makes a person gay. In fact, it's always been a bit of a joke in our family that my dad was responsible - he frequently dressed me up as a girl. In fact, he has some cross-dressing in his own past. He once dressed up as a tarty neighbour, pretended to crash his own party, and proceeded to flirt with the men in the room- all with my mum playing along for the laughs.
Nature or nurture?
The show actually gave me an opportunity to discover whether or not I had ancestors who were gay because years ago if you were in the closet you were so far in the closet you were in the house next door.
John Barrowman: The Making of Me
During the filming of the programme, I not only revisited my childhood, I was also subjected to a battery of psychological and physical tests, everything from comparing my DNA to that of my straight brother, Andrew's, to watching my brain light up like a fireworks display in response to certain erotic stimuli.
I've always been convinced I was born gay (and am happy that way). But over the years there are plenty of people who have argued the opposite - and some still do today. I really wanted to meet people like this, and the film gave me a chance to do so. In the unresolved argument about whether it is nature of nurture that makes us gay or straight, I was hoping for affirmation that nature decides. The risk I took in filming was that it would be disproved.
But in the end neither happened as the tests didn't provide that clarity. I learned that science has yet to find a fool-proof and definitive genetic test for gayness - at least in my case.
Yet I did find something unexpected and different. The latest science is concentrating on a whole new area of potential causality that I hadn't thought about at all. It's not genes, but it is biological, looking at hormonal effects in the womb.
Attracted to women? Barrowman's Captain Jack character flirts with Billie Piper
Other psychological and physical tests told me more about my sexuality. Like whether I had any latent attraction to women at all. That one really caught me by surprise - at least for a moment. And in word association tests, men tend to be more factual and literal. But women and gay men tend to be much more descriptive and eloquent. I'm glad to say that was true for me as well.
Another test involved looking at moving images of different combinations of men and women. I had to press buttons to signal my reaction while lying in an MRI scanner which also measured my reaction so I couldn't lie.
I'm proud to say that in some of the tests I was totally off the scale.
So participating in this programme was exciting and provocative, but in the end, taking the personal risk to discover what makes me gay was worth it because on a daily basis I get letters from young men and women who are feeling the brunt of our culture's homophobia. If exploring this issue can bring comfort to some of these young people then I think the programme will have done a really wonderful thing.