Britain's likely answer: Singapore, sea control, and blockade

Rather than seek an immediate fleet duel, the Royal Navy's broad plan would send a fleet to Singapore, secure its communications, and then move north as supply and local control allowed. Unlike a single-purpose plan such as the American War Plan Orange, British planning had to cover Germany, Italy, and Japan alone or in combination, so this was an adaptable sequence rather than a rigid script. Town-class cruisers and fast battlecruisers would raid Japanese commerce while T-class submarines guarded passages through the South China Sea. Possible advance positions included Hong Kong, Taiwan, the Philippines, and Weihaiwei, depending on American participation and local control. The strategic purpose is to preserve British trade while forcing Japan to spend scarce fuel defending routes and responding to raids.