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Dollis Hill research station
Britain's first speaking clock (shown) was tested at the Post Office's Dollis Hill Research Station in 1935. Dollis Hill subsequently worked with Bletchley Park on Colossus, the world's first full electronic computer.
After World War II, the Speaking Clock network was also used as a key component in HANDEL, the country's nuclear attack warning network. If you called the clock at just the right time — nine o'clock in the morning, precisely — you could hear the pips change frequency: this was part of the automatic testing of the system. HANDEL was turned off in 1992.
Image credit: BT