An Allied Japanese carrier fleet against Italy

Where would the Royal Navy employ Japan's fleet if Japan joined the Allies in 1940?

The Mediterranean is the likely first target, where combined carrier strikes could cripple the Italian Navy and accelerate the defeat of Axis positions in North Africa.

The answer moves the earlier Allied-Japan counterfactual from diplomacy to operations. Combining British and Japanese carriers would create a powerful 1940 striking force in the Mediterranean. A British night attack on Taranto followed by a Japanese dawn strike could leave little effective Italian fleet strength. Securing the sea more quickly would protect Crete, shorten the North African campaign, and let Britain concentrate more heavily against Germany.