At the GPO telegraphy office, 1874.

Plate taken from the 'Illustrated London News' (Vol 74/2 p 504). The Central Telegraph Office (CTO) was transferred from Telegraph Street to the General Post Office (West) on 4 February 1874. Originally intended as a headquarters building, the CTO gradually occupied practically the whole building by the early 1890s; the increasing popularity of telegraphic communication was reflected in the growth of the number of staff and quantity of equipment required to meet this demand. A fifth floor was added to the building in 1884. Various methods of telegraphy are being demonstrated, including the Hughes method', named after David Hughes (1831-1900) who invented the microphone.