Photos uncovered by the (UK) National Archives show how the police spied on the suffragettes. These covert images - perhaps the UK's first spy pictures - have gone on display to mark the centenary of the votes-for-women movement.
Surveillance pictures revealed: How the police kept watch
Ninety years ago, a Scotland Yard detective submitted an unusual equipment request.
It was passed up the chain, scrutinised, reviewed and finally rubber-stamped in Whitehall itself. Scotland Yard duly became the proud owner of a Ross Telecentric camera lens. And at a cost to the taxpayer of £7, 6s and 11d, secret police photographic surveillance was born.
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Spy pictures of suffragettes revealed