Junya Ishigami’s hillock of Cumbrian slate was meant to feel ‘primitive and ancient’. But British regulations – and the wind – dashed his dreams. Is it time to rethink the annual event?

this year’s Serpentine Pavilion is an enigmatic arrival to Kensington Gardens. Formed from hundreds of pieces of rough Cumbrian slate piled up in a gentle mound, it has the look of a bird hunkered down in a hollow in the landscape, making a protective shelter with its outstretched wings. As you approach, you find the great feathered hill is in fact a thin shell, 62 tonnes of slate effortlessly held up on a forest of slender white columns, creating a cave-like space within...[+]