The BT Tower is a grade II listed communications tower in Fitzrovia, London, England, owned by BT Group (formerly British Telecom). It was also known as the GPO Tower and the Post Office Tower, and later officially renamed the Telecom Tower. The main structure is 581 feet (177 m) high, with a further section of aerial rigging bringing the total height to 620 feet (189 m).

Upon completion in 1964, it overtook the Millbank Tower as the tallest structure in London until 1980, when it was overtaken by the NatWest Tower. It was opened in 1965 by Prime Minister Harold Wilson. A 360° coloured LED screen near the top of the tower displays news across central London.

In February 2024, BT Group announced the sale of the tower to MCR Hotels, who plan to turn it into a hotel. BT will retain ownership for a few years until the tower has been vacated.

The tower was commissioned by the General Post Office (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 General Post Office microwave network. It was to be built by end of 1963, and cost £1.5M, on Howland Street.

It replaced a much shorter steel lattice tower which had been built on the roof of the neighbouring Museum telephone exchange in the late 1940s to provide a television link between London and Birmingham. The taller structure was required to protect the radio links' "line of sight" against some of the tall buildings in London then in the planning stage. These links were routed via other GPO microwave stations at Harrow Weald, Bagshot, Kelvedon Hatch and Fairseat, and to places like the London Air Traffic Control Centre at West Drayton.

The tower was designed by the architects of the Ministry of Public Building and Works: the chief architects were Eric Bedford and G. R. Yeats. Typical for its time, the building is concrete clad in glass. The narrow cylindrical shape was chosen because of the requirements of the communications aerials: the building will shift no more than 25 centimetres (10 in) in wind speeds of up to 150 km/h (95 mph). Initially, the first 16 floors were for technical equipment and power. Above that was a 35-metre (115 ft) section for the microwave aerials, and above that were six floors of suites, kitchens, technical equipment, a revolving restaurant, and finally a cantilevered steel lattice tower. To prevent heat build-up, the glass cladding was of a special tint. The construction cost was £2.5 million.

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." Construction reached 475 ft by August 1963. The revolving restaurant was prefabricated by Ransomes and Rapiers of Ipswich. The steel lattice was made by Tubewrights Ltd of the Kirkby Industrial Estate (established in 1952, after it moved from Newport in Monmouthshire), owned by Stewart's & Lloyd's.

The tower was topped out on 15 July 1964, by Conservative MP for Norwich South, Geoffrey Rippon. It was officially opened by the then Prime Minister Harold Wilson on 8 October 1965. The main contractor was Peter Lind & Company. The company was founded in 1915 by Danish Peter Lind (he died aged 66 in Surrey in December 1966), headquartered on Watling Street in Cannock.

The tower was originally designed to be just 111 metres (364 ft) high; its foundations are sunk down through 53 metres (174 ft) of London clay, and are formed of a concrete raft 27 metres (89 ft) square, 1 metre (3 ft) thick, reinforced with six layers of cables, on top of which sits a reinforced concrete pyramid.

The stainless steel clad windows were made by Henry Hope & Sons, of Halford Works, Smethwick.

The tower was officially opened to the public on 19 May 1966, by Postmaster General Tony Benn (then known as Anthony Wedgwood Benn) and Billy Butlin, with HM Queen Elizabeth II having visited on 17 May 1966.

As well as the communications equipment and office space, there were viewing galleries, a souvenir shop and a revolving restaurant on the 34th floor; this was called The Top of the Tower, and operated by Butlins. It made one revolution every 23 minutes. Butlins were given the lease to restaurant in November 1963; it would open by the end of 1965. The section above the microwave dishes had two observation floors, a tea bar, a revolving restaurant, a cocktail bar, and above that a kitchen. At the top was a pulley room and above that the left motor room and ventilation plant. There were sixteen equipment floors between 115ft and 355ft. The restaurant was called 'Top of the Tower', where meals were about £4.

In its first year the Tower hosted just under one million visitors and over 100,000 diners ate in the restaurant.

A set of two stamps, designed by Clive Abbott (born 1933), 3d and 1/3, was issued on 8 October 1965 for the new tower, which had followed a set of stamps in the previous month for the 25th anniversary of the Battle of Britain. The stamps also featured Nash Terrace.

A bomb exploded in the roof of the men's toilets at the Top of the Tower restaurant at 04:30 on 31 October 1971, the blast damaged buildings and cars up to 400 yards (370 m) away. Responsibility for the bomb was claimed by members of the Angry Brigade, a far-left anarchist collective. A call was also made by a person claiming to be the Kilburn Battalion of the IRA. That act resulted in the tower being largely closed to the general public.

The restaurant was closed to the public for security reasons a matter of months after the bombing in 1971. In 1980, Butlins' lease expired. Public access to the building ceased in 1981.

The tower is sometimes used for corporate events, such as a children's Christmas party in December, BBC's telethon Children in Need (Children in Need 2010 was hosted from the tower), and other special events; even though it is closed, the tower retains its revolving floor, providing a full panorama over London and the surrounding area.

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.

In 1969, eight university teams competed, with John Pearson from Manchester University winning in a time of 5 minutes, 6 seconds.

The first microwave link would be to Norwich on 1 January 1965. The Met Office put their weather radar on the top. Much of the telecommunications equipment made by GEC of Coventry.

Due to its importance to the national communications network, information about the tower was designated an official secret. In 1978, the journalist Duncan Campbell was tried for collecting information about secret locations, and during the trial the judge ordered that the sites could not be identified by name; the tower could only be referred to as 'Location 23'.

It is often said that the tower did not appear on Ordnance Survey maps, despite being a 177-metre (581 ft) tall structure in the middle of central London that was open to the public for about 15 years. However, this is incorrect; the 1:25,000 (published 1971) and 1:10,000 (published 1981) Ordnance Survey maps show the tower. It is also shown in the London A–Z street atlas from 1984.

In February 1993, the MP Kate Hoey used the tower as an example of trivial information being kept officially secret, and joked that she hoped parliamentary privilege allowed her to confirm that the tower existed and to state its street address.

The tower is still in use, and is the site of a major UK communications hub. Microwave links have been replaced by subterranean optical fibre links for most mainstream purposes, but the former are still in use at the tower. The second floor of the base of the tower contains the TV Network Switching Centre which carries broadcasting traffic and relays signals between television broadcasters, production companies, advertisers, international satellite services and uplink companies. The outside broadcast control is located above the former revolving restaurant, with the kitchens on floor 35.

A renovation in the early 2000s introduced a 360° coloured lighting display at the top of the tower. Seven colours were programmed to vary constantly at night and intended to appear as a rotating globe to reflect BT's "connected world" corporate styling. The coloured lights give the tower a conspicuous presence on the London skyline at night.

In October 2009, a 360° full-colour LED-based display system was installed at the top of the tower, to replace the previous colour projection system. The new display, referred to by BT as the "Information Band", is wrapped around the 36th and 37th floors of the tower, 167 m (548 ft) up, and comprises 529,750 LEDs arranged in 177 vertical strips, spaced around the tower. The display was the largest of its type in the world, occupying an area of 280 m (3,000 sq ft) and with a circumference of 59 m (194 ft). The display is switched off at 10:30pm each day. On 31 October 2009, the screen began displaying a countdown of the number of days until the start of the London Olympics in 2012. In April 2019, the display spent almost a day displaying a Windows 7 error message.

In October 2009, The Times reported that the revolving restaurant would be reopened in time for the 2012 London Olympics. However, in December 2010, it was further announced that the plans to reopen had now been "quietly dropped", with no explanation of the decision. 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.

The BT Tower was given Grade II listed building status in 2003. 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 the removal of the defunct antennae was approved in 2011 on safety grounds, as they were in a bad state of repair and the fixings were no longer secure. The last of the antennae was removed in December 2011, leaving the core of the tower visible.

Entry to the building is by two high-speed lifts, which travel at a top speed of 1400 feet per minute (7 metres per second (15.7 mph)) and reach the top of the building in under 30 seconds. The original equipment was installed by the Express Lift Company of Northampton, but it has since been replaced by new 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. 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.

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. 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.

On 21 February 2024, BT Group announced the sale of BT Tower to MCR Hotels, who plan to preserve the tower as a hotel.

The tower has appeared in various novels, films, and television shows including Smashing Time, The Bourne Ultimatum, Space Patrol (1962), Doctor Who, V for Vendetta, 28 Days Later and it's 2007 Sequel, The Union and Danger Mouse. It is toppled by a giant kitten in the 1971 The Goodies episode "Kitten Kong", a parody of King Kong. It was also the title of jazz band, the Dudley Moore Trio's track "G.P.O. Tower", from the soundtrack to the feature film Bedazzled (1967), directed by Stanley Donen, where it also appeared on screen.

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  BT Tower under construction in the 1960s
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  View of the British Museum and the Thames from the BT Tower, 1966
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  BT Tower in 1970
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  BT Tower from Queen's Tower, 2007
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  Top of BT Tower from the London Eye

• List of masts
• List of tallest buildings and structures in Great Britain
• List of towers
• List of tallest buildings and structures in London
• Telecommunications towers in the UK
• Telecom infrastructure sharing

• "Connected Earth: Learning Centre". Archived from the original on 6 April 2005. Retrieved 21 January 2015.
• BT Tower (1964) at Structurae. Retrieved on 21 January 2015.
• "Peter Lind and Company – Building Contractors". Archived from the original on 29 April 2007. Retrieved 29 April 2007.
• Post Office Tower
• The official tower guide, archive film footage, and more.
• "The Tower from Conway Street QuickTime Panorama, British Tours ltd". Archived from the original on 18 January 2013. Retrieved 21 January 2015.
• "BT Tower photo feature on urban75". Retrieved 21 January 2015.
• 320 gigapixel panoramic view
• "Thirty-six Views of a London Tower..." A short film with the BT Tower in every shot.
• BT Tower building information & photos

Records
Preceded by Millbank Tower	Tallest Building in the United Kingdom 1967–1980 177 m	Succeeded by NatWest Tower
Preceded by Millbank Tower	Tallest Building in London 1967–1980 177 m	Succeeded by NatWest Tower