The BT Tower, formerly also known as Post Office Tower and London Telecom Tower, is located in the West End of the capital city. It was commissioned in 1961 and took 4 years to complete and was officially opened in 1965 by Prime Minister Harold Wilson. The structure measures a 158 ft (177 m) to the top, including its antenna 620 ft (189m), which made it the tallest building in the city until the NatWest tower was opened in 1981. Although the BT Tower is situated in the middle of the London and arguably of an impressive height and thus very visible, it was officially kept a secret and not shown on any maps, including Ordnance Survey maps, until it’s existence was “revealed” in 1993. The building is now Grade II listed and it’s newly added 360 degree colour LED screens display a countdown for the 2012 Olympic games. On the revolving 34th floor of the tower was a popular restaurant that was subject to a bomb attack in 1971 and closed down for security reasons in 1980, since 1981 the tower is closed to the public . In recent years it has been used for corporate functions but will now undergo refurbishment and is planed to reopen to the public in December 2011.