For much of his life, the British lawyer had been told that being gay somehow made him less of a man. Yet standing shoulder-to-shoulder with his gay teammates, he felt liberated. On the sports pitch at least, the ultimate judge of muscle wasn't sexuality -- it was the scoreline.
"I think I probably had a little bit of an inferiority complex growing up," says the 41-year-old, as we watch 70 young men train under the bright lights of an east London pitch on a crisp evening.
"So I really enjoyed playing rugby against straight men, with my gay teammates, because for me it kind of proved that we were just as masculine as they were -- that we can be just as physical as they are."
What started when six friends met in a bar in north London in 1995, with the idea of forming a gay-inclusive rugby team, has since turned into a club with over 150 members and three teams. The Steelers have won the European competition for gay rugby clubs, the Union Cup
, on four occasions.
Blood, sweat, and tears
How far have we really come in the last 20 years? As the 2015 Rugby World Cup enters its final stages, there are no openly-gay players in the tournament.
However, widely-respected gay referee Nigel Owens officiated in three pool games
and a quarterfinal, but is not involved in this weekend's semis. The Welshman came out in 2007 after a battle with depression which reportedly drove him to suicide.
He's not alone in his struggle -- former Wales captain Gareth Thomas became the first professional rugby player to publicly announced he was gay in 2009. Thomas, who retired in 2011, said he also considered suicide
under the immense strain it caused to his family life.
"It was such a positive message to send out because he wasn't just any old professional rugby player," says Bithell. "For somebody of his stature to come out was amazing."
More recently, when British rugby league player Keegan Hirst came out in August, he was hailed as a role model by the press
, and inundated with thousands of messages of support on Twitter.
But when the Kings Cross Steelers launched two decades ago, homosexual professional rugby players were unheard of.
This was 1990s Britain, and fear of the AIDS epidemic was actually enough to put some teams off playing the all-gay Steelers in such a high-contact sport.
"If you had said to me in the early '90s that out-gay men could play in a club like the Steelers, I'd have said it was incomprehensible," says the club's chairman, 43-year-old Alex Smith.
"The atmosphere was different back then. You have to remember there were AIDS adverts with tombstones."
Bithell says the homophobia they experienced in the early days wasn't only attributable to AIDS fears.
"A lot of teams just didn't want to play us," he recalls. "And you can never be sure why they declined.
"But I certainly experienced it as a player in particular when there was a blood injury. They would react in a completely hysterical way and start screaming 'Blood! Blood!' and screaming at the referee to get us off the pitch because they were afraid.
"It was the '90s -- people were still scared of HIV and there was a lot ignorance about how you could catch it and who could be infected."
Robert Hayward, a former Conservative MP and one of the club's founding members, remembers things differently.
Yes, he says, the team did keep the location of its first game secret until the last moment, out of concern they might be hounded by national newspapers. But from the very start they were openly accepted by the Rugby Football Union,
and he recalls only two players who ever refused to play against the Steelers.
"World Rugby had taken the decision a few years earlier that because it's a body-contact sport, anyone with a blood injury had to go off the pitch immediately -- and that was any player at any level," says the 66-year-old, who came out after he left parliament in 1992.
"But what was fascinating is that the players on the other side were almost less concerned about it than we were," he says, recalling one time he had a cut above his eyebrow -- another player actually wiped it away, telling him he was fine to stay on the pitch.
Smith says he can think of "maybe two homophobic incidents" in the last decade he's played for gay teams across the UK.
"We take the piss out of ourselves and there's nothing wrong with that -- it's part of rugby culture."
Smith first started playing rugby as an 11-year-old in Glasgow, Scotland, but by his mid-20s the gulf between his secret personal life and the straight teams he played for had become too great.
"I wasn't an out-gay man at that point and I found that increasingly difficult. We're talking the early to mid-'90s, and my teammates would be talking about what they were doing on Saturday night and I didn't feel I was able to do the same," he says.
"When I first played for a gay rugby club, I turned up, put on my boots, and it was exactly the same as any other rugby club I'd ever played for -- the difference was I felt I could be myself in a way I wasn't at other clubs."
Decades later, Caspar Swanston, who also played rugby growing up, says he joined the Steelers for much the same reason.
"I tried to join another club in London and I didn't feel completely comfortable," the 22-year-old explains.
"I wasn't openly gay. And there were a few comments, not directed at me but perhaps to the women who were in the park, which made me feel not feel like I wanted to reveal I was gay to them.
"And if I hadn't been told about the Steelers, I probably wouldn't have played rugby again for a very long time. Which would be a huge shame because it's something that means a lot to me."
Climbing the ladder
It took the team about a year to win its first game, and for Bithell this was an important turning point in the club's history.
"When we began we weren't a competitive team, we weren't very good. We were going into fixtures and we were losing by huge margins, and so we weren't being taken seriously as rugby players," he says.
"One of the best things that helped us was when we kept improving as a rugby club, and we kept improving the level of rugby. Even though in the early days we were still suffering heavy defeats, people could see that we were still serious about rugby and moving in the right direction."
Last season the club's first team continued its steady rise up the regional competitions, and now plays in the top tier of the London and South East Division's Essex League.
The Steelers are now also gearing up for the 2016 Bingham Cup,
the biennial international gay tournament to be held in Nashville, Tennessee, in May.
'People like me'
With over 50 gay rugby clubs around the world today, it's a long way from the days of six friends meeting in a London pub with a seemingly "incomprehensible" dream.
"We talk a lot about how much better or more inclusive the world is. And one question we're often asked is: 'Why are we needed?' says Smith.
"And the answer is people are looking for somewhere where people are like them. Rugby clubs are based around communities -- churches, schools, we're no different. We provide a safe space where people meet people like themselves."
The Steelers may have lost their first four games this season but, no matter the outcome of their next match, it appears they have already won a lot of respect.