Technical Block A, Heathrow Airport

Technical Block A at Heathrow Airport is a maintenance headquarters and office building constructed between 1950 and 1955 by Sir E Owen Williams for the British Overseas Airways Corporation, now occupied by British Airways. The building is primarily reinforced concrete with some brick facing to the offices, and has a flat asphalt roof. Designed to accommodate approximately 4,000 staff, it possesses a logical plan featuring a long range of offices along the south facade and a smaller range to the north, spanning five storeys. Between these ranges is a central, triple-height spine of engineering workshops, measuring 867 feet in length. This spine is flanked by four pens, identified as north, south, east, and west, with a further cross-axis of offices located between them.

The long southern entrance facade is characterized by a curtain wall of 42, 48, and 42 windows, set between concrete ribs and bands. Two entrances in the central section lead to staircases and the workshop spine. The north elevation presents a similar arrangement with 41, 42, and 41 windows punctuated by the pens. Three of the pens (excluding the south pen) were extended circa 1980 using a lightweight steel structure to accommodate larger operations; these extensions are not considered of special interest, nor do they detract from the structural value. Original office wall fenestration within the pens remains. The side walls display an 18-foot frame construction. Original entrances retain 336 spans bridged by cantilevers and a complex central beam, nine feet deep. Supporting the roof lights is a concrete roof of braced ribs. The South Pen retains its original folding doors, which, in conjunction with Williams's expressive cantilevers, contribute to a distinctive rhythmic composition.

The central workshop spine is a notable interior feature, showcasing an arched concrete roof supported by canted trusses, along with beams designed for moving cranes and balconies for the second and third floors. A second-floor board room, now designated Conference Room C, retains original panelling installed by the Design Research Unit. Original doors, identified by their varnished finish rather than paint, are present in some of the other office spaces.