Darth Wader has landed

It looks like something out of Star Wars. It moves, but does not use electrical power, nor engines of any sort. It transforms. It goes from pure form to pure function in a matter of minutes. But it's not from Hollywood, nor it is the latest invention by design-crazed Japanese or Korean. This technical wonder is from Marks & Spencer's headquarters at Paddington, London, Great Britain. It has been drawing steadily increasing crowds since its inauguration last year. It was designed by architect whiz-kid Thomas Heatherwick. Can you guess what it does?
Photos of the beauty...
... and this is how it works!