Prime Minister Harold Wilson opened the Post Office Tower in central London on 8 October 1965. At 620 feet high, including its mast, it was Britain’s tallest building. Wilson marked the opening by calling the Lord Mayor of Birmingham using the tower’s new microwave equipment.

The General Post Office had built the tower to increase the capacity of Britain’s telephone and television networks. Demand for long-distance telephone calls was growing, while television broadcasting was expanding. Installing additional underground cables into central London would have been expensive and difficult.

Microwave transmission offered an alternative. Signals could travel between aerials mounted on towers, as long as buildings did not obstruct their path. The Post Office needed a structure tall enough to transmit signals across London and stable enough to keep its directional aerials accurately aligned.

Construction began in June 1961. The tower was designed by the Ministry of Public Building and Works and built using concrete, steel and glass. Its narrow cylindrical structure became a distinctive feature of the London skyline.

Tony Benn, the Postmaster General, attended the opening ceremony alongside Clement Attlee, who had held the same office in 1931. After unveiling a plaque, Wilson and the other guests travelled to an observation gallery. Benn recorded that mist made it difficult to see across London.

Although the tower was operational in October 1965, it did not open to the public until 19 May 1966. Visitors could use the observation galleries and eat in a revolving restaurant operated by Butlin’s. More than a million people visited during its first year.

The tower continued operating as a communications centre while attracting paying visitors. A bomb exploded in the building in October 1971, causing damage but no injuries. The restaurant closed in 1980, and the public lost access the following year.