Music festivals are meant to be a bit disgusting. If you’ve never waded through ankle-deep mud to a festering, overused portaloo, have you ever really lived? This griminess has left its muddy footprints all over festival fashion, too. It’s Keira Knightley and Jamie Dornan in mud-splattered jeans, or Sienna Miller draped in a grey hoodie with an unlit cigarette drooping from her mouth. It’s weathered, functional and slightly undone.While British festivals conjurehellip;read more raquo;