Matt Hudson-Smith won his first World Championships medal, claiming 400m bronze with a gutsy run in Eugene.
The Briton, 27, went hard over the first 300m and then held off American rival Champion Allison and world record holder Wayde van Niekerk to take the final podium spot.
Michael Norman, of the USA, won gold in 44.29 seconds, ahead of Grenada’s London 2012 champion Kirani James.
“This is just the beginning,” Hudson-Smith, who ran 44.66, told BBC Sport.
“I don’t think I have scratched the surface, if anything. I have got a monkey off my back getting a world medal. Now I push on from here.”
In the wake of Norman’s victory, the American crowd cheered Sydney McLaughlin to 400m hurdles victory in a stunning new world record time.
It was on the same Hayward Field track that Hudson-Smith broke Iwan Thomas’ 25-year-old British record with a 44.35-second run in May.
However, the Englishman has always been adamant that he needs medals, not landmarks, at this point of his career.
At the age of 21, Hudson-Smith finished eighth in the Rio 2016 final, but came close to quitting the sport a year later, contemplating a career in strength and conditioning.
His mother convinced him to continue and he left his home city of Wolverhampton to train in the United States.
He missed last year’s Olympics with the latest in a string of medical problems, but has returned in fine form this season.
He qualified second-fastest for the final before finally adding another medal to his 2018 European gold.
“It’s mad,” he added. “I don’t think people know the half of it. These past three years have been a whirlwind – Achilles tendon tears, hamstring tears, a lot of mental health issues.
“I was just hanging on for dear life at the end there.”