Paul Butler has returned to light training to begin preparations for a potential undisputed fight with Naoya Inoue.

A showdown for all four world bantamweight titles is being discussed with both Butler and Inoue making it clear it is the fight they want next.

Butler was upgraded to full WBO champion in May after champion John Riel Casimero was stripped of the title over his weight struggles and inability to move forward with a mandatory defense.

While Japanese star Inoue added the WBC crown to his IBF, WBA belts, after destroying Filipino legend Nonito Donaire in two quick rounds last month in Japan.

Inoue is a huge star in his homeland, but Butler insists ‘Monster’ should be prepared to fight in the UK if he wants the chance to become undisputed champion.

The Japanese boxer is ready to fight in the UK if necessary, but may insist for the contest to take place on home soil. 

And though negotiations are ongoing between both camps, Butler is readying his body for a return to full training as he waits for the fight to be confirmed.

“I am back in the gym with my coach Joe Gallagher, five days a week at the moment, and I’m doing one session a day,” Butler said.

“I am just getting a base of fitness in ahead of a full return to training. I have not started to study Inoue as an opponent just yet but if the fight gets confirmed then he will be on my mind a lot.  I know it’s coming.”