Britain was Japan's closest ally at the time, and a primary sponsor of her naval armament. With a majority of the IJN at the time having either been designed or outright built in Britain, up to and including the famed Mikasa which would serve as Admiral Togo's flagship months later at Tsushima.

The fear then was that by some scheme either Royal Navy had helped Japan assemble a squadron and was operating with British support. Or through some hand waving had sold some of their ships to the Japanese and simply turned them over to their new crews, alleviating any need to secure new ships, order ones, or get some to the region. Or worst of all that given sufficient provocation that the British might decide to get off the sideline. The Anglo-Japanese Alliance would continue to deepen after the war, culminating really with the Kongo class battlecruisers. The ship was designed as basically an off shoot fo the British Big Cat family of Battlecruisers. The lead ship then was herself built by Vickers in Britain as well. It was only the post war acceleration of Japanese expansionism and the shifting geopolitics that led the UK to let the Alliance disintegrate in return for a closer relationship with the US.