[3] As an amateur competed in the men's welterweight event at the 2016 Summer Olympics and the 2015 European Games, in which he won a bronze medal, representing Great Britain.

[4] He is a supporter of Sunderland AFC[5][6] Having competed in the Olympics, Kelly's first fight as a professional was a six rounds points victory (59-55) against Jay Byrne (4-1) of Dublin in April 2017 at the SSE Hydro in Glasgow on the undercard of Ricky Burns vs. Julius Indongo.

[7] Kelly won his next two fights in the next two months, defeating Spain's Jony Vila (6-1) and Gateshead's Tom Whitfield (4-1) by fourth-round stoppage and first-round knockout respectively.

Kelly was struggling to handle Campos at times, but nonetheless managed to win the bout via unanimous decision, scoring 99-90, 99-90 and 98-91 on the scorecards.

[14][15] Kelly is the current British light middleweight champion after beating Troy Williamson by unanimous decision at the Newcastle Arena on 2 December 2022.