JAPAN• 269–J–JAPAN. MI5’s first case of Japanese espionage was that of Colin May-
ers, who was convicted under theOfficial Secrets Actin April 1927.
However, prior to that prosecution MI5 had maintained a watch on
Lord Sempill, a well-known aviator overtly employed by the Impe-
rial Japanese Navy as a consultant. No action was taken against him,
but in a similar caseFrederick Rutland, who had been kept under
surveillance for years and had had his mail intercepted, was arrested
under theDefence of the Realm Actemergency regulations in De-
cember 1941 because of his ‘‘hostile associations’’; he was detained
until September 1943 and committed suicide in January 1949.
MI5’s B1(f ) became aware of Japanese espionage in Britain in
June 1941 whentatewas instructed by hisAbwehrcontroller to
rendezvous on a London bus with a Japanese man. His contact was
followed bySpecial Branchand identified as Lieutenant Com-
mander Minitory Yosii, an assistant naval attache ́at the Japanese em-
bassy. Yosii returned to the embassy immediately after the meeting
and thereafter was kept under surveillance, but no further evidence
emerged of his activities as an Abwehr surrogate.
MI5’s review of Japanese espionage concluded that the Japanese
maintained an extensive intelligence network throughout the British
Empire through embassies and consulates, which concentrated with
ship movements and, in the United Kingdom, with bomb-damage re-
ports. The Japanese network was an important component of the Axis
intelligence system. MI5 identified Lord Sempill as a useful source
for the Japanese and noted that he had been connected for 10 years
with Mitsubishi, which paid him £300 a year. Following the outbreak
of war, Mitsubishi proposed stopping these payments, but at the spe-
cial request of the Japanese naval attache ́they continued for some
time, albeit at a lower level. In a letter on this subject, a director of
Mitsubishi described Lord Sempill as someone who was of ‘‘direct
and indirect benefit’’ to the military and naval attache ́s in London.
Lord Sempill had collected information on bombs and aviation for
the Japanese since 1925 and in 1930 was one of the two directors of
the Anglo-German Club.
Another Japanese source was Professor Grotwohl, a German by
birth with a British passport, his father having been naturalized in