Adam Peaty, 21, also broke his own world record to become the UK's first Olympic swimming champion for nearly twenty years.
He stormed to victory in 57.13 seconds to earn Team GB's first gold medal of the Rio Olympics, saying afterwards: "I did it for my country because that means so much to me".
"I want to thank the whole of Britain, my country, the Royal family and everything that makes me proud to be British."
Dr John Sentamu congratulated the Olympian on Twitter:
Peaty to be hugely congratulated for winning Olympic Gold and setting a new World Record.What an Olympian:he swims& breaks his WRs!God bless— John Sentamu (@JohnSentamu) August 8, 2016
Mr Peaty's record-breaking swim was followed just minutes later with a silver medal win for Team GB's Jazz Carlin, who took silver in the women's 400 metres freestyle.
The 25-year-old from Swansea (below) was heartbroken after missing out on selection for London four years ago.
She said after her triumph: "Four years ago I was in the stand cheering everyone on and now I've actually been a part of the team and to come away with a silver medal, I'm absolutely over the moon.
"I'm so grateful to everyone at home that's been supporting us and to get up and watch us at ridiculous hours of the morning."