The BH extension that never was and the Stronghold
by Andrew Emmerson

By the time the new Broadcasting House was in use it was clear that it was too small to house the rapidly increasing numbers of staff. Plans for an extension to be constructed to the rear of the building were made, and in July 1938 'Wireless World' was reporting that a start was about to be made at clearing the site then occupied by Nos. 10-22 inclusive, Portland Place, London, W.1. Demolition of the existing buildings, and clearing the site, would take several months, during which time detailed planning would be completed. It was hoped to have the building ready for occupation towards the end of 1940. The first photo shows the area of the proposed building marked in red. The familiar shape of All Souls Church can be seen to the right of BH, and behind the church is the Queen's Hall.

The new extension would more than double the size of BH. The site area at ground floor level was 20,950 square feet, compared with 17,390 square feet of the existing building. The architectural treatment, which was approved by the Royal Fine Art Commission, was planned to continue and amplify that of the existing facade to Portland Place, the two portions of the building forming a complete architectural entity that would be both dignified and in harmony with its surroundings.

Above ground level the building was planned to provide mostly office space. A new control room would be built on the seventh floor, meant to supplement, not replace, the existing one. A restaurant would be provided on the eighth floor with accommodation for nearly three hundred people. A light court would occupy the centre of the structure. Below ground level the plan provided a general purpose studio 80ft x 54ft by 30ft high, three dramatic studios, an effects studio and a number of rehearsal rooms. More than a million cubic yards of earth would need to be removed and the depth to which the building would go - fifty-four feet below pavement level - would be lower than the vaults of the Bank of England. The resulting excavation would have a capacity of nearly ten million gallons of water. By December 1938, 'Practical and Amateur Wireless' was reporting that Messrs. Higgs and Hill Ltd had been awarded the contract for the excavation and for the erection of retaining walls around the site, which had by then been cleared. This work would have been complete by about the middle of 1939. The first stage of the work was the opening of a trench around the site, some thirty feet wide and fifty-four feet deep, in which self-supporting retaining walls would be constructed to withstand all external pressure. Asphalt would face these walls and be returned, beneath them, and laid over the whole of the site. Five feet of 'loading concrete' would be superimposed upon it. The main structure, therefore, would virtually be built into a huge 'tank'. The lower part of the 'tank' would be below the standing level of sub­soil water, a fact which would demand special measures to ensure that the asphalt seal was perfect at the junction of the new 'tank' with that of the existing building, to compensate for settlement when the weight of the new building was taken upon the foundations. The plans were doomed, of course. The outbreak of war meant that construction of the new building had to be abandoned and it was to be another twenty years before an extension was built.

Instead, work started on what was to be a 'complete broadcasting station in miniature' built underground along Duchess Street. This structure was known as 'The Stronghold' and contained studios, a control room, recording rooms and offices, all under the shield of a concrete roof 9ft 6in thick.

Completed in November 1942 and linked by line and radio to transmitters at Brookman's Park and Daventry, the Stronghold was intended for emergency use - but fortunately it was never needed since although the main Broadcasting House was bombed on several occasions, it did not sustain damage serious enough to cause loss of programmes. The worst damage occurred on 15th October 1940, when a 500lb bomb landed in the music library, killing seven people. Bruce Belfrage, who was reading the nine o'clock news as the bomb exploded, paused briefly as he heard the noise and then finished the bulletin without stumbling. Several bombs subsequently left their mark on the outside of the building.

The Stronghold figured as a kind of last resort, along with Wood Norton (near Evesham, Worcestershire) in the BBC's planned scheme for evacuating studios. According to a document entitled 'Emergency Evacuation of London Premises', undated but almost certainly prepared in October 1942:

"The Stronghold and premises at Evesham are general reserves for all services. Within the limits of accommodation and facilities available, the Stronghold is a last reserve for any or all of the Corporation's services. It is also equipped so that Home News, News Talks and Presentation, could transfer to the Stronghold as soon as News Agency and Recording facilities were provided. (The Stronghold is reached through the gas-proof door, LG2, opposite the Lounge, on the lower-ground floor in the north-east corner of Broadcasting House. Keys are in the possession of the Duty Officer, Duty Room, B.23). Moves to Evesham or the Stronghold will be decided by the Director-General in the light of prevailing circumstances."

A total of 10,000 tons of concrete was used in the Stronghold's construction and it was designed from the outset to allow an extension of Broadcasting House to be built above later on. That said, it was an awkward structure to incorporate into later construction as the Stronghold is somewhat deeper than the lower ground level of Broadcasting House (one floor down from the ground floor and in fact above the level of the basement studios) but above the level of the basement of the BH Extension as eventually constructed. This was finally opened in 1962, although not to the elegant designs of 1938 nor on the same alignment. Built into the Stronghold is a door with a staircase leading down and ending in a brick wall, planned to give access to the basement level of the Broadcasting House extension originally intended. Incidentally, the Stronghold is the same protected accommodation that Peter Laurie described in Beneath The City Streets but mistakenly assumed to be at the Maida Vale studios.

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Notes by Andrew Emmerson, adapted from material in his book 'London's Secret Tubes' published by Capital Transport Publishing.

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At the time the Stronghold was built considerable thought was given to ensure that it could be incorporated into the BH Extension as it was being planned in 1937/8. My understanding was that the position of the Stronghold was that planned for the cashiers' office, which would require secure concrete walls similar to the construction of banks. The foundations of the Stronghold were planned to support the weight of the proposed superstructure of the Extension and consisted of 58 cored piles. The roof of the stronghold was augmented by a top layer of concrete blocks about 4x4x4 ft. with lifting eyes built into them so that they could be easily removed after the war.

In the late 1950s, when consideration was once again being given to an extension to BH, an agreement was reached with the Prudential Assurance Company for them to put up an office building and lease this back to the BBC. The Prudential was concerned that this should be treated as a separate office building which could be let to other customers at a later date if necessary. They would erect the shell of the building and the BBC would do the internal work to provide offices, control room etc., although studios were not originally included in the plans. During all the planning work no reference was made to a Broadcasting House Extension - it was referred to in drawings, memos, etc. as the 'Proposed Office Building Adjoining Broadcasting House' or 'POOBABH' in conversation !