Ok, so I've been having discussions with my mates (Rule Britannia), so I decided to come here. Please be aware I am usually a Pre-1900 guy and thus don't have the best knowledge of WW2.
Say, in 1939 (imagine Germany/Italy don't exist), the Japanese and Britain go to war, say over Hong Kong, Malaysia, etc. Alternate history stuff.
This never happened, as Germany/Italy got in the way, then America stepped in. So it was never truly a duel between the two Empires.
One on One, head to head, navally. Who would win?