Guardian Exchange was an underground telephone exchange built in Manchester in 1954. It was built together with the Anchor Exchange in Birmingham and the Kingsway exchange in London - all believed to provide hardened communications in the event of nuclear war. Today the underground site is used for telephone cabling. Constructed at a depth of 35 metres (115 ft), the tunnels are about 2 metres (80 in) in diameter. The exchange cost around £4 million (approximately £126 million in 2015 prices), part of which was funded by the United Kingdom's NATO partners.