In the autumn of 1925, workers were racing to erect a new arena in the Frederiksberg district of Copenhagen; it was due to open early the next year, with an international car exhibition. As Forum Copenhagen rapidly took shape, lighting manufacturer Louis Poulsen and young polymath Poul Henningsen were given just eight days to design the lights for the venue. Henningsen recognised that traditional overhead lamps would hammer the top surfaces of the cars with harsh light while leaving the sides in darkness, and so he drew up a version of the multi-shaded lamp that he had recently presented at a show in Paris. Three curved shades were carefully proportioned to diffuse a warm, glare-free light. The optimal relationship between the shades was calculated to be 4:2:1 for use in the exhibition space at Forum Copenhagen, but Henningsen and Louis Poulsen experimented with different proportions as they developed the design for use in other settings, and today the ‘PH’ lamp is offered in an array of sizes and finishes – each model giving off what Henningsen called simply ‘the right light’. £1250. louispoulsen.com