When Munich practice Betz Architects designed the German Embassy in Belgravia in the 1970s, security was not a major issue. The corner site, in Chesham Place, slopes steeply down to a mews at the rear and Betz took advantage of this by scooping out a double-height central well which greets you as you enter the embassy at upper ground level. A gallery running around the perimeter of the well leads to administration offices. The space below, meanwhile, is the visa section which, thanks to Betz's open plan became an integral part of the day-to-day life of the embassy.
Having taking over as architect to the German Consulate two years ago, one of Blauel Architects' recent refurbishment tasks has been to provide a security barrier between the lower public visa section and upper private spaces without compromising the openness of the original design.
An additional problem was light: the centre of the building is lit largely by artificial lighting and light fittings are hard to reach. As lamps failed, the visa section had become increasingly dark and cavernous.
Blauel's solution to the security issue is a series of tensioned wires strung across the void from new balustrade railings - like the wires of a grand piano.
Project architect Peter Jurschitzka explains that the idea came from observing a voliere at London Zoo. It is also indebted to the technology used in the bridge in the Materials section of the Science Museum, by the then Chris Wilkinson Architects. The structural engineer on both schemes was Whitby, Bird and Partners.
The glazed screen at the entrance of the embassy was raised to the same level as the glass gallery balustrading. Parallel stainless steel hollow circular sections are supported on the balustrade glazing and take the full pressure of the tensioned wires (a single rail would have had to be too large). The slender wires are strung across the void, 75mm apart. One end is attached to a phosphor bronze peg on a flange welded to the inner rail; it travels across the void, loops around ss pegs on the opposite rail and back to be secured and tensioned by another phosphor bronze peg. Installing the wires kink-free and fully tensioned was a painstaking operation. The wires still retain some slack.
New light fittings (complete with long-life Phillips lamps to minimise maintenance) reflect off the wires and produce highly visible moire patterns when viewed from the gallery. From the visa floor they are visible only as patches of reflected light, an effect similar to that produced by gauze curtains on a stage - appropriate in a building inspired by the drama of human interaction in a more carefree political climate.
CLIENT The German Embassy ARCHITECT Blauel Architects STRUCTURAL ENGINEER Whitby , Bird and Partners MAIN CONTRACTOR Henry Brothers (Magherafelt) SUBCONTRACTORS AND CREDITS SUPPLIERS wire McGrath Brothers; Limited; lamps Phillips; light fittings Lunar Lighting Ltd; glazing BSF Limited; steelwork McGrath Brothers