BT Communication Tower

Summary

A landmark communications tower designed by the Ministry of Public Buildings and Works and the Post Office in around 1954 and built between 1961-1965. The tower was London's hub in a national communications network and was previously known as the Museum Radio Tower, Post Office Tower, Telecom Tower and most recently as the BT Tower.

Reasons for Designation

The BT Tower is listed at Grade II for the following principal reasons:

Architectural Interest:

* for its innovative structure and distinctive sculpted silhouette designed to provide the stability, height and equipment necessary for its function;
* as a landmark building on the London skyline, the tallest when constructed, with its slender profile and Modernist detailing noted internationally;
* for the publicly accessible spaces, providing far-reaching views across London, and features such as the former restaurant's revolving floor.

Historic Interest:

* as London’s hub in a national network that transformed post-war telecommunications across Britain, designed by a team of architects and engineers led by the Post Office and Eric Bedford of the Ministry of Public Buildings and Works.

History

In the early 1950s, as telephone use soared, it became increasingly difficult to provide adequate cable links in central London and the Post Office began to consider developing a national network of microwave radio towers to serve growing telecommunication and television demand. Radio telephones using low frequencies had long been used, but the use of ultra-high frequencies was in its infancy. The commitment to the use of high frequencies on a potentially massive scale necessitated the development of a transmitter network to carry a microwave system across the country. The Howland Street Museum Telephone Exchange (excluded from the listing) was part of that evolution. A mast had been added to the roof and it functioned as the switching centre in London for the interconnection of outlets to the existing national radio and television network from numerous television studios in the London area including Broadcasting House. It was also the London focal point for microwave radio links for increasing telephone traffic.

The projected extent of the network by the 1970s necessitated the construction of new facilities across the country. A network of concrete towers was envisaged, most comprising a reinforced concrete, hollow cylinder built to standard designs by the Ministry of Works. A tower in London was needed as a focal point for the network and from the early 1950s, to meet the capital’s role as a hub of national and international telephone communication by ultra-high frequency (UHF) microwave transmission. Other communication towers constructed as part of this network include that in Stokenchurch and Birmingham; none are listed.

The design of the tower was overseen by Eric Bedford, Chief Architect for the Ministry of Public Building and Works (MPBW), the senior architect was G R Yeats assisted by C A E Thatcher and F G Micklewright. Post Office engineers employed by the Ministry of Works included L R Creasy, S G Silhan and H C Adams. The earliest model of 1956 was a square tower with a large podium base, evolving to a circular tower with aerials, transmitters and receivers at the top. Approvals for the tower were secured by February 1961; its simplicity of design and form were determined by specific technical requirements. A circular plan allowed signals to be transmitted through 360 degrees and the materials used had minimal interference with signal strength. The tower would have a glazed public viewing platform at 460ft (140m). The sensitive equipment meant that the tower had to be exceptionally stable to maintain the accuracy of the narrow beam transmitters. By means of tests in the National Physical Laboratory wind tunnel, it was stiffened to deflect only eleven inches in a hundred mile an hour gale and stabilised by a bridge deck or collar which tied the tower to the podium building. The cylindrical shape reduced wind resistance.

The design of the tower had broadly three distinct sections, the equipment floors, the aerial floors and the public floors, and underwent numerous iterations before construction started, including a staggered design to the upper floors to accommodate a restaurant with a revolving floor and observation platforms. The inclusion of restaurant facilities was part of a movement across North America and central Europe in favour of landmark restaurants connected with radio masts. However, the comparable, slightly earlier towers at Dortmund, Stuttgart and Vienna were only television transmitters, and the Space Needle at the Seattle World's Fair (opened 1962) was principally a place of entertainment.

Construction started by June 1961. The height was raised to over 580 feet (177m) as building commenced, in order that the tower should be taller than the office buildings then being erected in London. The contractors were Peter Lind & Co and the building was completed in 1965. The tower was at the forefront of international design and carefully considered for its elegance, representing ‘a considerable advance on any existing international centre' (Institution of Civil Engineers, 1965, p 33). The Architects' Journal, (22 June 1966, p 1543) considered that 'the massing is a very welcome addition to the urban landscape'. The tower was opened by the Prime Minister, Harold Wilson, and Anthony Wedgewood Benn, Postmaster General, in October 1965. In an accompanying leaflet Benn noted that ‘as landmark, symbol, centre of a modern telecommunication network and a magnet for visitors, the tower sums up our time.’

The upper floors of the tower suffered from bomb damage in 1971. Subsequently, the observation floors were closed to the public and in 1980 the restaurant closed too. Several phases of renovation took place in the 1980s,1990s and early-C21.

Eric Bedford (1909-2001) was the Chief Architect to the Ministry of Public Buildings and Works between 1950 and 1970, the Government body which oversaw the design, construction and maintenance of public buildings from the Second World War until 1970. He was a committed modernist, leading on numerous projects including the British Embassy in Washington D.C and the Post Office Tower in Birmingham, opening in 1966 as part of the communication system which had the BT Tower at its heart. The London BT Tower is arguably the best-known building designed by Bedford’s team, although the delivery of numerous housing and civic schemes, such as the Grade II-listed Queen’s Court Building at the Royal Courts of Justice, (National Heritage List for England entry 1469797) attests to their technical expertise.

The Podium Building (known as the West Block in 2026), also designed by the Ministry of Public Buildings and Works, was a flexible space for offices, open at the ground floor for car parking along the Maple Street and Cleveland Street elevations.The exterior and interior were remodelled in the 1980s, 1990 and early C21. It is excluded from the listing.

The former Museum Telephone Exchange was designed by Frederick Allen Llewellyn and constructed in 1936. It was remodelled after the tower was built with additions to the rear and roof, with exterior and interior alterations. It is excluded from the listing.

Details

BT Tower, proposed 1954, built 1961-1965, designed by the Ministry of Public Buildings and Works (MPBW) Architect's Department; Eric Bedford Chief Architect, G R Yeats, senior architect in charge; S G Silhan, senior engineer MPBW, structural engineer; J J Taylor, senior engineer MPBW, services engineer; Kenneth Holloway, Post Office engineer.

MATERIAL: reinforced concrete structure and floors, board mark finished to lower 130ft (40m) with stainless steel triple curtain wall glazed with Antisun glass.

PLAN: sleek cylinder split into three distinct sections: the former equipment floors, the aerial floors and the public floors, each element expressed in the exterior architectural treatment of the building. The circular shape, dictated by the aerials, provided minimum wind resistance.

EXTERIOR: tower with 20ft (6m) deep raft foundations, a shaft 582ft (177m) high, with 40ft (12m mast) on top. Total height is 620ft (around 190m). At the fourth floor, a concrete collar (not mapped) provides stability to the tower.The lower five floors (used formerly for ventilation, battery and refrigeration plant) and the eleven floors above (which held radio and equipment racks) are clad in triple external curtain wall. Above are the former aerial floors on circular galleries, exposed externally to provide maximum flexibility for adjustment and new equipment. The dishes (most removed) had to be mounted between 365ft (111m) and 475ft (145m) to achieve adequate ground and obstacle clearance. The upper, cantilevered section about 22ft (7m) in diameter and with walls 1ft (0.3m) thick, taper outwards to about 35ft (11m) external diameter at base with 2ft (0.6m) thick walls and comprise about 103ft (32m) of staggered hospitality floors at the top of the tower, on six levels with glazed curtain walling. Three further storeys housing plant are above.

INTERIOR: at the tower’s core are lift lobbies accessing the pair of high-speed lifts and a stair; the lifts were renewed in the early C21. All floors are structured around the tower’s core, the lifts serving all floors.

The lower sixteen floors are largely devoid of equipment in 2026, most being redundant or removed. On floor 14 some late C20 equipment and desks remain. The equipment floors have inserted ceilings, exposed equipment trunking, metal panelling, plain rendered walls to the core and some lino floors. All doors are late-C20.

The six former public levels include observation floors (levels 31-33); the former 65ft (20m) diameter restaurant floor (floor 34) which originally revolved once every 25 minutes; cocktail bar (level 35) and kitchen (level 36). The rotation gear remains on floor 34, but the interiors of all public floors have been refurbished and retain no historic features and finishes.

At basement and sub-basement level, the tower’s pyramidal foundation is exposed. The foundation is included in the listing but is not mapped.

Pursuant to s1 (5A) of the Planning (Listed Buildings and Conservation Areas) Act 1990 (‘the Act’), it is declared that the Podium block, former telephone exchange, and all servicing and communications equipment are not of special architectural or historic interest. However any works which have the potential to affect the character of the listed building as a building of special architectural or historic interest may still require LBC and this is a matter for the LPA to determine.

Legacy

The contents of this record have been generated from a legacy data system.

Legacy System number:

490152

Legacy System:

LBS

Sources

Books and journals
Creasy, L R, Adams, H C, Lampitt, N, Museum Radio Tower in Institution of Civil Engineers, Vol. paper 6822, (1965), 33-78
Radio Campanile in Architectural Review, (August 1965), 123-126
Post Office Tower in Architect and Building News, (25th May 1966), 939-44
Building Illustrated: GPO Tower in Architects' Journal, (22nd June 1966), 1537-49
The Post Office Tower in The Journal of the London Society, Vol. 377, (December 1966), 107-116
Swain, T, Stephen Croad Prize Essay 2024: A Twenty First Century Re-evaluation of the Iconic BT Tower in Journal of Historic Buildings & Places, Vol. 4, (2025), 123-144
Official Architecture and Planning in The Builder, (7th August 1961), 265-8
Cherry, B, Pevsner, N, Buildings of England, London 4: North, (2002), 262

End of official list entry

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