The 30-year-old took the prize on Saturday in Glenrothes, Fife, with a points win over Casey Blair, of Belfast, whom he knocked down twice.
But the fight could not be sanctioned as the official Celtic Light Heavyweight crown, as Blair was over the regulation weight. The bout was also truncated from 10 rounds to six, then to four, for reasons John says were not fully made clear.
However, the win put him back to the top of the rankings, as he still beat a credible opponent, and he hopes his uncrowned status will enable him to challenge for the UK title.
This will be contested between Joshua Buatsi and Liam Conroy on March 23 at London’s Copper Box Arena.
John, who has a finance degree and spends time in Melrose and Galashiels, said: “I felt good going in and felt the preparation was well on target, with the right approach. It all paid dividends on the night. It was a positive perfomance.
“It was target practice, really – everything I threw, I landed. I found my range and distance from the start. Casey, to the respect of him, came to win that fight, and he came out swinging.”
Women boxers accounted for the rest of the bill in Fife – jointly making John the first ever male boxer to contest a professional show with an all-female undercard.
He is currently training at Guildford City Boxing Club in Surrey, while he has been sparring in Brighton with the Eubank brothers – Sebastian and Chris Eubank Jnr.