The school is a rectangular block with a hollow centre. A school hall used to divide this central space, a hall that was, as de Rijke admits, the most architecturally interesting bit of the original building. It was about the only part that showed the deft touch of its well-regarded architect of the time, Sir Leslie Martin. But the hall could not accommodate all the pupils and it was in the way, so de Rijke demolished it. Then - this sounds so easy - he covered over the resultant single huge courtyard with an inflatable translucent roof. It is made of the same material as the Eden Project's bubbles, but is rather more sophisticated, its layers embossed with an interference pattern that creates dappled shade inside. It has a deliberately op-art effect as you walk around. In very bright sunlight, the roof can automatically darken by deflating slightly to merge two of its three layers.

De Rijke's second move was to abolish the corridors, replacing them with broad first-floor walkways down the two long sides of the courtyard. These in turn are linked by an angled bridge across the centre. Not only does this mean that all the pupils can be seen and accounted for as they move around, but it means that they and the teachers can orientate themselves. Even de Rijke used to get lost in the building. Better still, they are not just walkways. Like the courtyard below, they are lined with seating for pupils and staff to gather and chat. Before, there was nowhere to meet except in classrooms.