Jenny Beavan is possibly the first woman to receive an Oscar wearing an M&S jacket and comfy shoes. She talks to Eva Wiseman about fashion, feminism and that Vine videoEvery good plot needs an antihero, and this year’s was costume designer Jenny Beavan, who caused a series of small explosions when she accepted first a Bafta, and then an Oscar, wearing not the regulation diamond gown but a pleather jacket from Marks & Spencer and a pair of comfy shoes.Today in Peckham, in her first sit-down interview since the furore, the most rebellious force in Hollywood is making me a cup of tea.