Commonwealth House, New Oxford Street, London

Corners can be the most interesting parts of a building. From medieval castles with their mural towers onwards, how a structure makes the transition from one plane to another can tell you a lot about the building’s purpose, or its builders’ priorities. Early builders often emphasized the corner’s strength with buttresses, extra-large quoin stones, or those castle towers. But in the skyscraper age, when the structure became a hidden metal frame and the wall a ‘skin’ of glass, the priorities changed – the glazing could go right up to the corner, glass meeting glass with little or no visible means of support. Art deco buildings sometimes even had panes of glass that curved through 90 degrees, dissolving the corner completely.

But here’s a skyscraper-age building that turns a corner with emphasis. Commonwealth House is sited where New Oxford Street and High Holborn meet at an acute angle. The architect, H. P. Cart de Lafontaine, placed a round tower at the junction, a tower banded with windows and topped with a modernist clock face. It was built in 1939, and like a lot of buildings from the 1930s it’s a mixture of steely modernism – strip windows and lots of them, the numberless clock face – and, elsewhere on the building, restrained detailing drawing on Art Deco motifs. But this circular tower, placed at a major junction, is a cut above the norm, a landmark for a new age that was about to be stopped with a jolt in its tracks.