Callum Simpson is ready to put his ‘career on the line’ in an immediate rematch with Troy Williamson which has been pencilled in for May 2.

Simpson (18-1, 13 KOs) was stunned by underdog Williamson as he attempted to make what many had predicted would be a routine defence of his British, Commonwealth and European super-middleweight titles on December 20.

Williamson (22-4-1, 16 KOs), one of British boxing's best servants over the past decade, ripped up the script and stopped Simpson in the 10th round of their clash at Leeds’ First Direct Arena.

As Williamson had been a voluntary defence for Simpson, a rematch clause was included in the fight contract and now the 29-year-old from Barnsley has decided to trigger it, his promoter Ben Shalom confirmed on Tuesday.

“We have activated it and that fight will happen in May, 100 per cent,” Shalom said.

“It’s a huge rematch, Callum’s career is on the line and he knows that. He has made a few changes, he will announce them soon, but it’s a huge night for both of them.”

The initial fight happened in Simpson’s home county of Yorkshire, around 25 miles away from his home, but when asked whether Darlington’s Williamson will now enjoy home advantage as champion, Shalom said: “The fight will be wherever we want.

“To be fair, Callum gave Troy a voluntary shot and we gave him the opportunity of a lifetime. I was glad for Troy Williamson, I love it when fighters have had a really tough time and have had to come from different ways. It was an unbelievable story.

“For me this would still be the biggest pay day for him. It’s not a jail sentence, he gets a massive night against a fighter he’ll believe he will beat again. I’m looking forward to that, probably back in Yorkshire.”

It had been suggested that Simpson may decide to rebuild in a different way before attempting to win back his belts down the line but Shalom is adamant the new challenger had no choice but to head straight back into the fire against Williamson.

He added: “He had the rematch clause and if he lets that go, maybe he never gets the opportunity again. I believe he knows where he went wrong.”