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SIGINT IN THE SUN - GCHQ'S OVERSEAS EMPIRE 151
followed, with the diplomats accusing the Special Branch of
bending the evidence, while the policemen accused the diplomats
of a lack of trust. The issue of exactly how close the MCP
was to Peking was never resolved. 6
GCHQ's most important outpost in Asia was Hong Kong. China
was the venue of one of Britain's early Cold War code-breaking
triumphs. Between March 1943 and July 1947 GCHQ was able
to read the high-grade Russian cypher traffic passing between
Moscow and its mission at the headquarters of Mao Tse-tung's
People's Liberation Army in Yunnan. This was a highly secret
programme, and GCHQ only began passing material to the
Americans in March 1946. The decision not to share until this
point may have reflected anxieties about the strong differences
within the American administration about China policy, but it
is noticeable that the spring of 1946 also marks the advent of
the revised BRUSA agreement. 7 Exactly how this breakthrough
was achieved when many other Russian high-grade cypher
systems remained immune to attack is still a mystery. However,
SIS had placed a rather eccentric officer called Michael Lindsay
at Mao's headquarters in Yunnan, where he was assisting the
Chinese Communist communications team as their 'principal
radio adviser'. This may eventually prove to be part of the story.8
The British colony of Hong Kong was of special value to the
United States. This reflected the fact that, after the end of the
Chinese Civil War that brought Mao Tse-tung to power in 1949,
the United States did not even have an embassy in mainland
China. 'Hong Kong became an American watchtower on China,'
recalls Jack Smith, who looked after the Far East in the CIA's
Office of National Estimates. 9 GCHQ joined with the Americans
and the equivalent Australian organisation, Defence Signals
Branch, to develop the facilities in Hong Kong. Washington
received the full intercept output of Hong Kong, but with the
onset of the Korean War demands for intelligence went up
sharply, and Washington considered that combined US-UK intercept
facilities in the Far East were 'far short of requirements'. 10