Surveillance image of a Suffragette prisoner

Surveillance image of a Suffragette prisoner exercising in the yard of Holloway prison taken by an undercover police photographer. Handwritten on the back is ‘Lillian Ball’. However it is likely the image is of Editha Warwick Ball who was sentenced to 6 months imprisonment in Holloway in February 1913 for smashing 8 windows in London's West End.
Scotland Yard undertook covert photography of militant suffragettes from 1913. The images were used to identify suffragettes attempting to enter public buildings such as museums and art galleries, where they might attempt to damage the objects.