Heat the oven to 180C. Grease and flour a 9" pie dish. Rub oil over whole of the inside of the dish, bottom and sides. Roll out the pastry to fit then place in the tin. Flatten pastry into bottom and sides thoroughly. With excess pastry over the sides take a rolling pin and roll over the edge of the dish to get a lovely neat edge and remove the excess. Prick the bottom with a fork all over.