As the soaring 3,312-piece glass roof celebrates its 20th birthday, its creators recall the risks, setbacks, and unexpected discoveries – and that time Nelson Mandela paid a visit
It’s hard to imagine now, but the courtyard at the centre of the museum used to look like a mini Manhattan. It was cramped with multilevel concrete buildings that housed the book stacks for the British Library. They were joined by walkways at different levels, and an internal labyrinth of corridors. Demolishing this whole structure was the riskiest and most complicated part of the whole project – they turned out to be much better built than anyone had expected.