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Home of the Speaking Clock

The former post office building that helped crack the code.


This was the home of the Post Office Research Station from the 1920's to the 1970's. This station was dedicated mainly to research in telecommunications and the teams at Dollis Hill played a leading role in a number of key advances in the field.

In 1914, the Postmaster General agreed that the Post Office needed improved facilities for research and that a permanent Engineering Research Station should be established. In 1919 the Treasury agreed to buy this site in Dollis Hill. Initially, staff worked in wooden ex-army huts until the permanent buildings had been completed. The main research building opened in 1923.

In 1936, the Speaking Clock - known to London users as TIM - was designed and constructed there by Dr E.A. Speight.

The Dollis Hill teams were also responsible for the development of the Trans-Atlantic telephone cable and for providing the links for outside television broadcasts, such as the first broadcast of the Remembrance Day service in 1937.

The site also played a role in the deciphering of the German Enigma code during World War II. Tommy Flowers put his Colossus computer together here, and later reassembled it at Bletchley Park.

Location: Flowers Close, Brook Road, Dollis Hill