In the 2016 World AC Championships held at the National Croquet Center, West Palm Beach in Florida, he defeated Christian Carter, Stephen Forster, Danny Huneycutt, and Reg Bamford before reaching the final.
Bamford, having won the World Championship on four previous occasions, was a favourite to win and took the first two games in the best-of-five match decisively, but Mulliner scraped through in the third game, took the fourth with a sextuple peel that nearly went badly wrong, and then took the fifth game with convincing form.
In the final match against David Maloof (USA), Mulliner again went 2-0 down, but scraped a victory in the third game to remain in the match and then played solidly to take the last two games.
The victory made Mulliner the oldest world champion at 62 (he had reached the final on two previous occasions, in 1997 and 2008).
Outside the world of croquet, Mulliner had a City career and is now a management consultant and a Conservative local councillor.