Find a pretty glass dish for serving the trifle. You will also need a measuring jug, a saucepan, a wooden spoon and a small bowl for mixing the jelly and the custard.
Break the sponge cake into pieces and place in the base of the serving dish. Drain the mandarin oranges, keeping the juice, and put a few oranges aside for decoration. Place the remainder in the dish with the sponge cake.