Make the jelly, pouring each colour in a separate medium-sized greased bread pan. Place in the fridge to set.
Once the jelly has set, loosen the sides with a knife. Turn the mould over and the jelly should flop out.
Cut the Swiss roll in thin slices. Place a layer of the cake in the bottom of the mould. Sprinkle some of the sherry over the cake. Then place a layer of the solid jelly. Pour custard over the jelly. Spread a thin layer of whipped cream over the custard. Sprinkle nuts over the cream. Repeat the layers until the mould is full. Place in the fridge to set overnight.
Remove the trifle from the fridge. Using your serving dish, place it over the mould. Turn it upside down, and the trifle will flip onto the dish. Using the leftover cream, pipe it onto the trifle and garnish with the strawberries.