Complex sentence: In the autumn of 1940, Britten was summoned to the Japanese consulate, where he was read a long letter from Prince Konnoi, brother of the prime minister of Japan, who served as organizer of the celebration.
Split into simpler sentences: In the autumn of 1940, Britten was summoned to the Japanese consulate. There, he was read a long letter from Prince Konnoi, brother of the prime minister of Japan, who served as organizer of the celebration.