“I hadn’t changed. It wasn’t about who I went to bed with or what sexuality I was. I was still me.”

Standing 6ft 6in with a body that seems custom-made for the pool, he was – and still is – one of the most recognisable names in British swimming.

He was the man who made world records tumble, racking up world, European and Commonwealth titles in a career that spanned 23 years and five Olympic Games.

But there was also a part of Foster that the public didn’t see.

“My home life was my own secret life, which enabled me to go out and just be ‘Mark the swimmer’,” the 51-year-old says.

“Probably because I seemed big enough, strong enough, ‘manly’ enough, I kept the questions away. It was sport – and sportspeople aren’t gay, right?”

Except, of course, they are – and Foster is too.

Five years on from sharing his sexuality with the world, the swimmer has been speaking to the BBC’s LGBT Sport Podcast about what he has learned – and how times have changed.

‘There were no sportspeople to look up to’

Foster was told to learn how to swim by his father, who himself had nearly drowned when he was pushed into a river as a schoolboy.

But in reality, his son was always likely to end up in the pool.

“I felt at home in the water, and I’ve got the right physique for it,” Foster says.

“I’m 6ft 6in and would have been rubbish at gymnastics, but I suited swimming.”

That physique was paired with a determination, even at an early age, to keep improving his times in the water.

And after a young Foster watched Britain’s Duncan Goodhew win 100m breaststroke gold at the 1980 Moscow Olympics, he knew that swimming was what he wanted to do.

And yet, away from the pool, other feelings began to emerge.

“I knew as a 13-year-old that I was a little bit different,” Foster admits.

“But all I ever heard – at school, in the newspapers, wherever I went – was that being gay was not right.

“That’s me, and I’m being told it’s not normal. And there were no sportspeople I could look up to and go: ‘Well, that’s me and I’m like them.’

“So I just got used to shutting down that side of me, and I started juggling and living two separate lives.”

‘I had that little voice where I was afraid of what people might say’

For the entirety of his professional career, there were two Marks.

One was the charismatic competitor who became a world champion six times as well as winning two Commonwealth Games gold medals and 11 European titles, as well as breaking a host of world records.

“It was about medals and making teams, but it was always about improvement,” Foster says.

“My world record in the 50m freestyle was in the shortest event with the fastest stroke – so if you’re that world record holder, you’re the fastest person on the planet through water. That’s pretty cool!”

That was the Mark who went to five Olympics and who, at his last Games in Beijing in 2008, had the honour of carrying the British flag into the Bird’s Nest Stadium for the opening ceremony.

“I kept pinching my hand while I was carrying it,” the swimmer smiles.

“I was thinking about how this moment would never happen again, and it was humbling.”

But there was also the other Mark who – after coming out to his mum – was determined not to let anyone outside of his family know about his sexuality.

“I had that little voice where I was afraid of what people in swimming might think, afraid that they might not want to share a room with me,” Foster says.

“I was the big, strong one on the team, the muscly one who did the cool event. I was captain, and wasn’t going to put myself up there to be shot at or worry about what they might or might not think.

“So I just got used to hiding my private life.”

‘I’m just thinking: You’re seeing Catherine, she lives in Cambridge’

Like many LGBTQ+ people, Foster became an expert in blurring the lines in his personal life in order to keep his sexuality under wraps.

“I used to tell my swimming mates I was going home to see ‘Catherine’,” he says.

“She was a friend’s wife who I knew a lot about, so I had an easy backstory.

“I remember at the 1995 European Championships in Vienna, being in a hotel room with all the lads. The boys were going round the room, talking football and general stuff, and the topic of who you’re seeing came up.

“And I just remember sitting there thinking: ‘You’re seeing Catherine, she lives in Cambridge.’

“I’m not even listening to what’s going on. I’m just sitting there, hoping that I’m not going red, thinking: ‘Don’t start sweating.’

“I was sort of trapped in my head with stories.”

‘I had to do my bit’

Neither retirement from active competition nor a successful stint as a pundit during the BBC’s coverage of the London Olympics made Foster any more willing to open up about being gay.

Appearing as a contestant on Strictly Come Dancing had brought him to the attention of a wider audience, but was also accompanied by unwelcome intrusion from newspaper journalists who wanted to know about his private life – which, if anything, made him more determined to keep his sexuality out of the public eye.

And while the swimmer had began to trust some of his close friends with his secret, it wasn’t until November 2017 – at the age of 47 – that he felt comfortable enough to share it with the world.

“I became really good mates with Clare Balding, Gareth Thomas, Tom Daley,” Foster says.

“And hearing that in certain countries, there is still the death penalty [for LGBTQ+ people] – and that even in the UK, people still get beaten up and called names – I thought: ‘Why don’t you stand up?’

“By adding my weight, it might help someone in another part of the world, it might help someone in the UK… I had to do my bit.”

‘I was still Mark – and if you can go with love, you get love back’

With that decision to finally speak publicly, the ‘two Marks’ had become one – and, five years on, Foster is equally comfortable talking about his sexuality as about his swimming.

It’s a remarkable turnaround for a man who spent an entire professional career determined to keep the two things apart.

So does he think times have changed when it comes to LGBTQ+ inclusion in sport, and does he wish he’d done anything differently?

“It’s polar opposites to where we were when I was a kid,” Foster says.

“There’s a lot more people out there being themselves, which is brilliant. But then again, you see in the news that someone is being beaten up for being gay, so we have a way to go.

“I don’t think there’s a right or wrong time for people to come out. I was 47. Do I wish I was 15? Yeah, I do, if I had my time again – but I don’t.

“But I found out that my friends were my friends.

“I always thought they wanted to hang out with me because I was ‘Mark the swimmer’. But actually, they liked hanging out with me because of who I was, and I hadn’t changed.

“It wasn’t about who I went to bed with or what my sexuality was. I was still Mark, who is stupid and childish and likes chatting a lot, but loves people.

“And if you can go with love, you get love back.”

Mark Foster was speaking to Jack Murley on the BBC’s LGBT Sport Podcast. You can hear new episodes every Wednesday on BBC Sounds.