The Old London Underground Company started proceedings regarding the future of The Kingsway telephone in 2009.
The exchange didn't start life as a telephone exchange. It started life as the Chancery Lane station on the Central London Railway underground line, built between Shepherd's Bush and Bank, and opened on July 30th 1900. Forty years later, Chancery Lane station was designated one of the city's "deep shelters" designed to withstand the onslaught of the Blitz during WW2, opening in March 1942 and providing safe shelter for up to 8,000 people at a time.
In 1945 it became the home of the Public Records Office until they ran out of space two years later, and had to find an alternative home. So in 1949 it was agreed that what had been the Chancery Lane station/deep shelter should become a new home for the Post Office's main telephone exchange. This required more excavation, extending the tunnels and enlarging the premises to accommodate what was called "a telephone city under London".
Opening for business in 1954, 100 feet below street level, the Kingsway trunk exchange was a fully self-contained, air-conditioned home for its 200 workers complete with restaurant and bar. It had its own water supply from an artesian well, and fuel tanks that held enough to keep the generators going for six weeks. Automatic routing was provided for over 6,000 calls at any one time, and also provided the "hot line" that connected US and Russian presidents during the Cold War.
What's more, between its opening in 1954 and 1966, the Kingsway exchange remained completely secret. Even in the 1980s its full use remain discreet, and it wasn't until the late 1990s that it was decommissioned and finally, in 2008, became surplus to BT's requirements.