A police informer in 1926

There's been lots of recent controversy about police spying on radical movements (including the case of 'under cover in East Dulwich'), but of course the practice is nothing new. During the 1926 General Strike, an informer was unmasked in Lewisham, as Roger Geary recounts in his book 'Policing Industrial Disputes: 1893 to 1985' (Cambridge University Press, 1985):

'As well as raiding the premises of publishers and arresting Communists there is some suggestion that Special Branch officers acted as agent provocateurs. For example, a mysterious sympathiser seemed rather anxious to supply the Westminster Strike Committee with ammunition. The Committee was convinced that the man was a police agent. Similarly Lewisham Council of Action suspected a man called Johnstone, who was the local secretary of the Unemployed Workers Committee Movement, of being a police informer. Their suspicions turned out to be justified for when Johntone committed suicide shortly after the strike both his wife and his mistress admitted that he had been in the pay of Scotland Yard. His mistress revealed that Johnstone had occasionally invented the reports he had sent to his masters and that once the police had challenged the authenticity of the information he was providing. After this incident Johnstone, not unreasonably, became convinced that there was at least one other police informer in the London District Countil whose reports were being compared with his'.