A British World War I hero worked as an agent for Japan's espionage service between 1933 and 1941 as Tokyo prepared for war with the United States, according to security service files recently released by the British government.

Fredrick Joseph Rutland worked for Japanese intelligence services while living in Britain and Los Angeles, and was paid around 3,000 British pounds (in 1930s prices) per annum, according to the declassified documents.

The former air officer regularly kept in touch with his bosses at the Japanese Embassy in London, and the personal files show for the first time -- through decrypted Japanese cipher traffic -- the depth of his relations with Japan, where he was described as an "active" agent under the code-name "Shinkawa."

According to the declassified files, Rutland informed Tokyo via his contacts that the U.S. had no immediate plans to interfere with Japan's aggression toward China.