was formed which took over the operation of the cables and built a cable office in Porthcurno valley. The concrete cable hut, where the cable shore ends were connected to their respective landlines, is a listed building and still stands at the top of the beach. ETC and its cable operations expanded through the late nineteenth and early twentieth centuries, in 1928 to merge with Marconi's Wireless Telegraph Company Limited to form Imperial and International Communications Limited which was renamed Cable and Wireless Limited in 1934. Cable and Wireless Limited was a predecessor company of Cable & Wireless Worldwide and Cable & Wireless Communications. In the inter-war years, the Porthcurno cable office operated as many as 14 cables, for a time becoming the largest submarine cable station in the world, with the capacity to receive and transmit up to two million words a day. Porthcurno is still known colloquially by the acronym 'PK' being represented in Morse code as 'di-dah-dah-dit' followed by 'dah-di-dah', communicating with a line operator and testing connections, an acronym often sent. Over the years, many apprentices were trained at the Porthcurno cable office in telegraphy and supporting skills, initially by ETC and then by Cable and Wireless. In 1950 the latter, nationalised, opened its Porthcurno engineering college which provided many courses in branches of telecommunications for employees, secondees and external students. The cable office closed in 1970, exactly 100 years after the first cable was landed, but the college remained open, receiving substantial investment in buildings and training equipment through the 1970s and 1980s; however, due to its isolation from towns, it closed in 1993. Some of its buildings were demolished. After the closure of the college, the award-winning Porthcurno Telegraph Museum was opened. This museum has been featured locally and nationally on educational programmes, including the BBC TV documentary series What the Victorians Did for Us and Coast. It occupies some of the former college buildings and includes many exhibits, in 'The Tunnel'. World War II tunnels The cable office at Porthcurno was a critical communications centre and considered at serious risk of attack during the Second World War, being only about from the port of Brest in occupied France. To improve security, a network of two parallel tunnels, connected by two smaller cross-tunnels, was bored into the granite valley east side by local tin mining labourers, starting in June 1940, to accommodate the essential