The second ballot opened yesterday with a chance to win a place in dining at the iconic restaurant at the top of the tower.

Diagram of the BT Tower’s floors, 1960s.

Post Office Tower under construction, 1963.

BT Tower under construction, 1964.

BT Tower in 1966

Diners in the BT Tower restaurant, 1966. The restaurant was closed to the public in 1980 for security reasons.

The Post Office Tower as seen from Fitzroy Square, London, 1967.

View of Post Office Tower from Rathbone Street, London, 1969.

The Post Office Tower, London, 1960s.

Damage after a bomb exploded in the Post Office Tower, 1971.

BT Tower souvenir postcard.

BT Tower at dawn, 1985.

BT Tower during the London 2012 Olympic and Paralympic Games.