BT Tower

Design and construction

The tower was commissioned by the GPO. Its primary purpose was to support the microwave aerials then used to carry telecommunications traffic from London to the rest of the country, as part of the GPO microwave network.[8]

It replaced a shorter, 1940s steel lattice tower on the roof of the neighbouring Museum Telephone Exchange. The taller structure was required to protect the radio links' line of sight against tall buildings then planned in London. Links were routed via GPO microwave stations Harrow Weald, Bagshot, Kelvedon Hatch and Fairseat, and locations including the London Air Traffic Control Centre.[9][10]

The tower was designed by the Ministry of Public Building and Works, under chief architects Eric Bedford and G R Yeats. Typical for its time, the building is concrete clad in glass. The narrow cylindrical shape was chosen as a stable platform for microwave aerials. It shifts no more than 25 cm in wind speeds of up to 150 km/h (95 mph). To prevent overheating, the glass cladding had to be tinted.[11]

Construction began in June 1961; owing to the building's height and its having a tower crane jib across the top virtually throughout the whole construction period, it gradually became a very prominent landmark that could be seen from almost anywhere in London. A question was raised in Parliament in August 1963 about the crane. Reginald Bennett MP asked the Minister of Public Buildings and Works, Geoffrey Rippon, how, when the crane on the top of the new Tower had fulfilled its purpose, he proposed to remove it. Rippon replied: "This is a matter for the contractors. The problem does not have to be solved for about a year but there appears to be no danger of the crane having to be left in situ."[12] Construction reached 475 ft by August 1963. The revolving restaurant was prefabricated by Ransomes & Rapier[13] and the lattice tower by Stewarts & Lloyds subsidiary Tubewrights.[14]

The tower was topped out on 15 July 1964, by Geoffrey Rippon[15] and inaugurated by Prime Minister Harold Wilson on 8 October 1965. The main contractor was Peter Lind & Company.[16]

The tower was originally designed to be just 111 m high; its foundations are sunk down through 53 m of London clay, and are formed of a concrete raft 27 m square, 1 m thick, reinforced with six layers of cables, on top of which sits a reinforced concrete pyramid.[17]

Initially, the first 16 floors were for technical equipment and power. Above that was a 35 m section for the microwave aerials, then six floors of suites, a revolving restaurant, kitchens, technical equipment, and finally a cantilevered steel lattice tower. The construction cost was £2.5 million.[11]

The first microwave link was to Norwich on 1 January 1965. The Met Office put a weather radar on top of the tower.[18] Much of the telecommunications equipment was made by GEC.[19] The stainless steel clad windows were made by Henry Hope & Sons Ltd.[20]

Opening

The tower was opened to the public on 19 May 1966, by Postmaster General, Anthony Wedgwood Benn and Billy Butlin,[21][22] with HM Queen Elizabeth II having visited on 17 May 1966.[23]

As well as communications equipment and office space, there were viewing galleries and a souvenir shop. Butlins' Top of the Tower revolving restaurant on the 34th floor made one revolution every 23 minutes[24][25] and meals cost about £4[26].

In the first year there were nearly one million visitors,[27] and over 100,000 diners.[28]

Bombing

A bomb exploded in the ceiling of the men's toilets at the Top of the Tower restaurant at 04:30 on 31 October 1971;[27] the blast damaged buildings and cars up to 400 yds away.[29] Responsibility for the bomb was claimed by members of the Angry Brigade, a far-left anarchist collective.[30] A call was also made by a person claiming to be the Kilburn Battalion of the IRA.[31]

The tower was closed to visiting by the general public following the 1971 bombing, but the restaurant reopened. In 1980, Butlins' restaurant lease expired.[32]

The tower has been used for events including a children's Christmas party and Children in Need 2010.[33] It retains the revolving floor.[34]

Recent

The tower's microwave aerials remain in use into the 21st century, connected to subterranean optical fibre links.[35]

In 2009, a 360° coloured screen was installed 167 m up, over the 36 and 37th floors of the tower. It replaced an earlier light projection system and incorporated 529,750 LEDs arranged in 177 vertical strips around the tower. It was then the largest of its type in the world,[36] occupying an area of 280 m2 and with a circumference of 59 m. It displayed a countdown of the number of days until the start of the 2012 Summer Olympics.[37][38]

In April 2019, the screen broadcast a Windows 7 error message for almost a day.[39]

In October 2009, The Times reported that the revolving restaurant would be reopened in time for the 2012 London Olympics.[40] However, in December 2010, it was noted those plans had been "quietly dropped".[41]

For the tower's 50th anniversary, the 34th floor was opened for three days from 3 to 5 October 2015 to 2,400 winners of a lottery.[42]

The BT Tower was given Grade II listed building status in 2003.[43] Several of the defunct antennae attached to the building were protected by this listing, meaning they could not be removed unless the appropriate listed building consent was granted. Permission for their removal was given in 2011 on safety grounds, as they were in a bad state of repair and the fixings were no longer secure.[44] The last of the antennae was removed in December 2011, leaving the core of the tower visible.[45]

Entry to the building is by two high-speed lifts, which travel at a top speed of 1400 feet per minute (7 m/s) and reach the top of the building in under 30 seconds. The original equipment was installed by the Express Lift Company, but it has since been replaced by elevators manufactured by ThyssenKrupp. Due to the confined space in the tower's core, removing the motors of the old lifts involved creating an access hole in the cast iron shaft wall, and then cutting the 3-ton winch machines into pieces and bringing them down in one of the functioning lifts.[46] In the 1960s an Act of Parliament was passed to vary fire regulations, allowing the building to be evacuated by using the lifts – unlike other buildings of the time.[47]

In 2006, the tower began to be used for short-term air-quality observations by the UK Centre for Ecology & Hydrology and this has continued in a more permanent form as BT Tower Observatory, an urban atmospheric pollution observatory to help monitor air quality in the capital.[48][49] The aim is to measure pollutant levels above ground level to determine their source. One area of investigation is the long-range transport of fine particles from outside the city.[50]

On 21 February 2024, BT Group announced the sale of BT Tower to MCR Hotels, who plan to retain the tower as a hotel.[51][52][53]

Races

The first documented race up the tower's stairs was on 18 April 1968, between University College London and Edinburgh University; it was won by an Edinburgh runner in 4 minutes, 46 seconds.[61]

In 1969, eight university teams competed. John Pearson from Victoria University of Manchester was fastest in 5 minutes, 6 seconds.[62]

In May 1969, the tops of the GPO Tower and the Empire State Building in New York City served as the start and finish lines of the Daily Mail Trans-Atlantic Air Race. The race between the two buildings was held over an eight-day period and commemorated the 50th anniversary of the first non-stop transatlantic flight of Alcock and Brown. A total of 21 prizes were offered to entrants for categories based on the type of aircraft they utilised and their direction of travel.[63][64]