OPEN HOUSE: THE ROYAL COLLEGE OF PHYSICIANS

As part of Open House London, I visited the Royal College of Physicians yesterday. The RCP building in Regent's Park was designed by Denys Lasdun. We were ably guided by Calder Barnabas, who wrote his PhD on Lasdun.

Lasdun is better known for the National Theatre, but the RCP building is equally successful, closer to the International Style than the Brutalist National Theatre. Several of the ideas Lasdun used in the National Theatre were first tried in the RCP.

The Royal College of Physicians is an ancient body, founded in the reign of Henry VIII.  By the 1950s had become clubby, in an obscure location near Trafalgar Square, and a bit stuffy. But the president and council determined that it should it should modernise  and have a more public face. Overcoming the reluctance of the more conservative members, they chose Lasdun to design it. Some of the costs were met by the Wolfson Foundation and the RCP (whom Dr Barnabas described as ideal clients) instructed Lasdun not to skimp on the materials and finish for the sake of £15,000 here and there – remember this was the late 1950s.

Lasdun's building is Modernism at its best, its design determined by its intended use and shaped to facilitate the activities of the college. Although of a different era and style from the surrounding Nash terraces, it takes account of them, echoes their materials and colours and creates stunning views of them.

The central area of the college is open and airy, as captured in the photo (above) by Chris Guy. It's arranged on several levels linked by a staircase and giving views of the lower floors from the upper, offering a theatrical view of the activities there – something developed even further in the National Theatre. There is a huge glass wall looking out on the college garden and Nash's houses and made so as not to draw attention to itself but only to what can be seen through it. By this, Lasdun links the inside and the outside of the building. The glass panels were the largest that could be made in Britain at the time; now, fifty years later, we have lost the capacity to do so, and if they have to be replaced, they will have to be imported.

The building is faced in black brick and pale grey mosaic. The brick was commissioned from English brick makers. Although most of the building is rectilinear, part of it has a gently curving wall in the manner of Corbusier's Chapelle Notre Dame du Haut, for which Lasdun needed brick in several different shapes – and exceptional bricklayers too, I imagine. The bricks are uniform in colour, achieved by careful sorting on site and rejection of those that were the wrong shade. Other walls are faced with porcelain tesserae, commissioned from a tile maker in Italy  (presumably beyond the capacity of Stoke on Trent), in a colour chosen to match the paint used on the Nash stucco. Since then, the Crown Estate has changed the colour of its stone paint, so the point is now lost. The mosaic continues within the building, again uniting inside and outside.

The building has been treated with respect by the Royal College of Physicians. It's Grade I listed, but the respect goes beyond that. Unlike many other Modernist buildings, its interior hasn't been added to or cluttered up. The library and meeting rooms are almost free of furniture when not in use, in deference to Lasdun's wish. "Architects don’t like furniture," said Dr Barnabas.

The RCP building is open to view outside the Open House weekend.