It’s more than 40 years since gangling Neasden schoolgirl Lesley Hornby became Twiggy, the world’s first supermodel, almost over night. Her doe eyes and elfin crop defined Sixties London, and now that decade’s poster girl is turning 60 herself. The National Portrait Gallery is leading the celebrations with an exhibition and book dedicated to her career: her early years in fashion, her stint as a Broadway actress and singer, and her recent return to modelling as the mature face of M&S.