BT Tower: London’s Most Underrated Landmark  

Written by Sam Marks

Long before the Shard and the Gherkin graced London’s skyline, the BT tower reigned supreme as the tallest building in London from 1964 to 1980. At 189 metres, it was visited by millions of people per year who marveled at its then unparalleled height. However, despite being a tourist attraction, the BT Tower was officially a secret under UK law until 1993. How could a landmark so iconic that it showed up hourly in the Thames Television animated introduction possibly be a secret? Despite the absurdity, the official secrecy of BT Tower was directly related to why it was built.   

Built from 1961 to 1964 in Fitzrovia, London, the Museum Radio Tower, as it was originally called, was commissioned by the General Post Office (GPO) to relay telecommunications from London to the rest of the UK. Amid rising tensions during the Cold War, the GPO wanted to build a telecommunications tower that could withstand a nuclear blast. Construction was carried out by the Ministry of Public Building and Works whose chief architect, Eric Bedford, left the upper floors uncovered to show the microwave links in plain sight. Even in design, the Tower was not at all created with a sense of discretion.  

Prime Minister Harold Wilson officially opened the tower for operations on 8 October 1965. The Tower in London was built alongside a series of microwave transmitters built across the UK during the early 1960s. This was part of a project known as “Backbone”: a UK-wide radio relay network that would transmit telecommunications without the use of cables. Towers were built from southeast England all the way to Scotland with the aim of making communications more secure in the event of a nuclear war. The transmitters within the tower could handle 150,000 phone calls at once. Yet the Tower was not solely used for government purposes.  

A year after it was opened for operations, Postmaster General Tony Benn and holiday camp magnate Billy Butlin opened the Tower to the public. Quickly becoming a sightseeing mainstay, the Tower had a souvenir shop and viewing galleries of several of the non-technical floors. The thirty fourth floor was complete with The Top of the Tower, a revolving, high-priced restaurant operated by Butlins. It made one revolution every twenty-three minutes and served eight hundred lunches and one thousand and three hundred dinners every week. The thirty fifth floor was complete with a cocktail bar and a wide selection of drinks. Even when not attending the restaurant, an average of four thousand and five hundred people went to the observation deck beneath the restaurant to get a clear view of the London skyline. The Tower even hosted races up the stairs to the top floor. One race saw an Edinburgh University student beat a University College London student with a time of four minutes and forty-six seconds. So how did a landmark so well-known and open to the public officially remain a secret?  

Because the tower was built for government communication purposes, it was officially considered secret information under UK law. Falling under the Official Secrets Act of 1911, the Tower could not appear on official government maps and its address was not acknowledged by the government. Simply known as “Location 23”, Westminster was technically unable to discuss anything related to the Tower in public briefings. However, the Tower was unceremoniously formally declassified in 1993, when MP Kate Hoey used parliamentary privilege to confirm the existence of the tower. This made the Tower public information, to the surprise of no one. Unfortunately, its declassification came after the Tower was closed to the public.  

On 31st October 1971, a bomb exploded in The Top of The Tower. Responsibility was claimed by both the IRA and the Angry Brigade, a group of far-left anarchists. While the Tower was undamaged and repaired quickly, the observation decks were closed following the blast and the restaurant closed immediately, never re-opening. Since 1980, the Tower has remained closed to the public but remains in use as a telecommunications facility.  

In 1980, the BT Tower lost its position as the tallest building in London to the NatWest Tower and is currently the 22nd tallest building in London. Currently, its most noticeable feature is the spinning BT logo on a series of screens outside the Tower. While it’s a shame not to be able to see BT Tower in its glory days, there is still an incredible amount of intrigue into what is arguably the UK’s worst kept secret.  


Fox, Steve, and Richard Lamont. “Backbone Microwave Relay Network.” In Subterranea Britannica. Accessed December 24, 2022. 

GPO Tower Race To Top. Accessed December 25, 2022. 

How London’s Tallest Tower Was a State Secret, 2021. 

Lewis, Paul. “Eric Bedford, Who Changed London’s Skyline, Dies at 91.” The New York Times, August 13, 2001, sec. World. 

Look at Life – Eating High, 1966, 2011. 

Perkin, George and Cement and Concrete Association. Concrete in Architecture / [Editor, George Perkin]. London: Cement and Concrete Association, 1968. 

What’s the Greatest Machine of the 1960s…the Post Office Tower? (With Chris Barrie), 2021. 

Featured image credit: Agency, Property Services. English:  The Post Office Tower during Construction. between   and 1967 date QS:P571,+1961- -00T00:00:00Z/8,P1319,+1961-00-00T00:00:00Z/9,P1326,+1967-00-00T00:00:00Z/9 1961. Photograph medium QS:P186,Q125191. UK National Archives.

Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

Create a website or blog at

%d bloggers like this: