Olympic GOLD for Chorley's Anna Hopkin in mixed relay
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The original quartet of Kathleen Dawson, Adam Peaty, James Guy and Freya Anderson were more than two seconds clear of the rest of the field in the heats, setting a new European record, and Team GB, with the addition of Hopkin for Anderson, eased to victory on Saturday morning.
Hopkin replaced Anderson for the final freestyle leg and touched out in three minutes and 37.58 seconds for Britain's fourth gold in the pool at Tokyo 2020 and seventh gong overall - matching their tally from London 1908.
The time was 0.83 seconds better than the previous best benchmark of 3mins and 38.41ecs - set by China last year - while they finished 1.28secs clear of China, with Australia taking bronze.
This event has been added to the Olympics schedule for the first time - where two males and two females must be selected but the nation can use any combination in the backstroke, breaststroke, butterfly and freestyle splits.
It means the lead can change hands multiple times as men and women can race against each other in the same leg of an event that was first introduced for long course swimming at the 2015 World Championship.
Dawson started with the backstroke and her time of 58.8s meant Peaty leapt into the pool with Britain sixth, and the 100m breaststroke gold medallist's astonishing split of 56.78s helped them up into fourth.
Guy, who won his first gold earlier this week in the men's 4x200m freestyle relay, clocked exactly 50s in the butterfly to take Britain into the lead and Hopkin finished in 52s flat to spark exuberant celebrations.
Hopkin, 24, came into the race knowing she would go head-to-head against the men's 100m freestyle champion Caeleb Dressel but the American was well back as Britain touched out in three minutes and 37.58 seconds.
"It's pretty cool to say I've beaten Caeleb Dressel," said former Chorley Marlins swimmer Hopkin. "To know that he was coming for me, it's a little bit intimidating. But I knew that the guys ahead of me would get me a good lead.
"And then it was just about me focusing on my own race and keeping my head down, not worrying about where he was. Because that would just distract me, and stay focused on my lane and bring it home for the guys."
For Peaty and Guy it was a second gold medal of the games and Peaty said: "I hope this team and the rest of British Swimming get the recognition and the respect that they deserve because it's been hard.
"Honestly people don't understand how hard it is. Hopefully people back home can understand that.
"I've been doing this for seven years since 2014 and I didn't think the team would be where they are today. You've got such amazing talent. It's just incredible to be part of that and hopefully people back home are pretty pumped."
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