The Central Telegraph Office (CTO) was transferred from Telegraph Street to the General Post Office (West) on 4 February, a building which was begun in 1869 on the site of the present BT Centre in Newgate Street/St Martin's Le Grand. GPO West, as it was known, was constructed of granite and portland stone and was originally four storeys high. 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.
The CTO's role in the history of telecommunications is a significant one. The first London-Paris telephone service was controlled from here from 1891 and Marconi demonstrated his new system of wireless telegraphy on the roof of the building in 1896. In its heyday the CTO had direct communication with every large town in the UK and was the largest telegraph office in the world. At the peak of the telegraph service in 1945-46 it dealt with 64.9 million telegrams, compared to only 45,000 in 1880.
During wartime such an important communications centre was an obvious target, and the CTO suffered during both world wars. The damage in 1917 during the First World War was relatively minor, but the Second World War saw much more substantial damage; during a raid on 29 December 1940 the CTO was set alight by burning debris from adjacent buildings and the interior was totally destroyed. The shell of the building was refurbished to the first and second floors, and the unsafe upper floors dismantled. The building was reopened in June 1943, although by this time much of the telegraph work had been transferred to the outskirts of London.
Following the war, telegraphic traffic declined as more and more people turned to the telephone, and the CTO never regained its pre-war importance. It was gradually run down from 1959 as work was transferred to other locations and eventually closed in October 1962. It was subsequently declared unsafe and demolished in 1967. The site remained derelict for some years, presenting an ideal opportunity for excavations by the Department of Urban Archaeology of the Museum of London during 1975-1979, yielding much information on the earlier history of the site. Finally, planning permission was granted in 1979 for the construction of a new building: BT Centre, the present headquarters of BT, opened in 1984.
Jean Maurice Emile Baudot (1845-1903) invented the Baudot printing telegraph system using the multiplex principle suggested by Wheatstone. This was the first system to use a code consisting of five units of equal length.