Initially, it seemed Campbell’s time in the gym would serve the sole purpose of learning self-defence before moving to secondary school a couple of years later.
That was until he started competing in amateur competitions, slowly but surely becoming obsessed with his newfound escape from the difficulties he faced at school.
“I was quite a soft kid, in the sense that I didn’t really like the violence or the fighting,” Campbell said.
“I felt like when I did fight, and when I really did go into it, everything changed and I never looked back.”
Aged 15, he won his first international Muay Thai title and started to realise that, with the blessing of his parents, combat sports could become more than just a pastime.
“I was never the cleverest kid. I was always in the bottom sets at school, so I wasn’t really focused,” Campbell said.
“All of the teachers told me, ‘you need to do something else. You have to have a plan B.'”
But for Campbell, who was beginning to attract attention across Merseyside, his unwavering commitment to the sport meant there was no need for a back-up plan.
That included regularly running almost five miles to and from school. There was even one occasion when he missed school while studying for his GCSEs to attend a coaching seminar in Liverpool hosted by John Kavanagh – the coach of former two-weight UFC champion Conor McGregor.
After completing his GCSE exams at the age of 16, Campbell enrolled on a college course that combined studying for a qualification in sport with playing football.
Or at least that was what he was supposed to be doing.
Campbell struck an arrangement with the course leads that allowed him to attend classes before leaving to train in combat sports, while his peers were on the football pitch.
“I was always avoiding anything just for fighting,” Campbell said.
“I really didn’t like school. It wasn’t me. But I made a good few mates there, so you’ve got to take the pros with the cons.”