Sift the flour and baking powder into a large mixing bowl, add the remaining cake ingredients and beat with a wooden spoon until smooth.
Spoon the mixture into greased and base lined 2 x 20cm sandwich tins or one 20cm square cake tin.
Bake in a preheated oven for at 180°C/ Fan 160°C/Gas 4 for 30 minutes in the sandwich tins or 45 - 50 minutes in the square tin. Turn out on to a wire tray.
Put the fruit juice and sugar in a saucepan and heat gently until the sugar has dissolved. Whilst cake is warm, drizzle the syrup over so that it soaks into the cake.
When cold, split the square cake in half and sandwich together with half the Elmlea. Reserve some Elmlea for decoration and spread remainder over the top of the cake. Decorate with fresh berries in the shape of a Union Jack and pipe with remaining Elmlea to decorate.