‘She became very concerned with the lack of definition about what qualified as ‘subversive’.’

The Special Branch Files Project, a live archive of once-declassified files focussing on the surveillance of political activists and campaigners, was launched last week.

Set up in 1883 to help with combatting the threat of Irish republican terrorists in the reign of Queen Victoria, the Metropolitan Police’s Special Branch with time assumed a much wider role, monitoring the activities of anarchists, Bolsheviks and even the suffragettes.