Relief poured out of Adam Peaty after he became the first British swimmer to retain an Olympic title with a characteristically dominant display in the final of the men's 100 metres breaststroke.

While he was unable to break his own world record of 56.88 seconds, the 26-year-old from Uttoxeter stormed to Team GB's first gold of Tokyo 2020 by clocking 57.37secs, the fifth fastest time in the event's history.

His supremacy therefore remains unchallenged with closest challenger Arno Kamminga, the only swimmer other than Peaty to breach the 58-second barrier, finishing a distant 0.63s behind.

Peaty's coronation has seemed inevitable as not only is his personal best almost a second quicker than anyone else who has ever competed over the distance but he is unbeaten in major competitions in seven years.

But Peaty, who swore twice on the BBC in an emotional poolside interview in the moments after writing his name into the history books, admitted the past year, which has included becoming a first-time father, has had its upheavals.

He said: "It's been a heavy investment. A lot has changed this last year, more than the last five. Becoming a father, buying my first house and some days when I woke up and was like 'this is hard, this is really hard'.

"There's been so many challenges, so many challenges and f****** some breakdowns as well. It's like 'what am I doing every single day? Why am I training three times a day, giving it everything for this swim?'.

"I've hidden a lot of emotion from my own family, I've hidden a lot of stress and a lot of those moments where I was like 'this is very, very hard'.

"It's like going for a promotion and trying to prove yourself every five years in 56-57 seconds, it's like to trying to prove what you're worth.

"I don't think people back home would understand the amount of investment which has been put into this swim. For a lot of people they could lose it just in that last moment. For me that amount of investment has paid off.

"There's a lot of emotion, I'm probably not going to sleep for a while now, I'm so buzzed because that was the first British swimmer to ever defend a title. You can do what you want all year round; in your own arena, in your own backyard, it doesn't mean anything, it means everything here.

"The 99.9 per cent of time that we spend in the dark is for the 0.01 per cent we spend in light.

"That's something me and (coach) Mel (Marshall) have always believed in. That's why I don't think anyone deserves it more than me and that's not an arrogant thing."

Nicolo Martinenghi collected bronze in a time of 58.33s as Britain's James Wilby missed out on a podium position, settling for fifth as he clocked 58.96s, in a race where Peaty showed his enduring class from the off.

Asked whether he was disappointed he did not lower the benchmark over the discipline he has mastered for much of the last decade, Peaty responded: "No, I don't give a s*** about the time! No one thinks about times.

"Yes, it would have been amazing to finish on a world record but it's not about that and Mel said this morning 'it isn't about the time, it's about the race' and no one races better than me."

Peaty – who brought a gold medallion with him to the Japanese capital which reminds him of his son, George, who was born last September – read a letter his partner, Eiri, wrote the night before his historic gold medal.

Peaty, who could win a second medal in the 4x100m medley relay later this week, added: "The letter goes 'this is what it's about'. I've had some messages from home but I only choose to read a few because that's all I need.

"There's that film, The Last Samurai: too much mind, too much mind. All you've got to do is be present, be in the moment and enjoy it.

"You don't even have to think about the stroke, that takes care of itself, so I'm glad I can go home with at least one gold medal."