1. Reserve half of the raspberries for decoration, halve the rest and put into a bowl. Remove the stalks from the strawberries and chop them add to the raspberries.
2. Cut the cake into 2 mm thick slices then cut into 8 rounds to fit the diameter of the glasses you are using. Beat the mascarpone with the custard until smooth.
3. To assemble the trifles, place a round of cake in the bottom of each glass add a spoonful of fruit then squeeze over Lyle's strawberry syrup. Carefully add a layer of the cream mixture, repeat the layers then add the reserved raspberries on the top for decoration. Just before serving dust with icing sugar.
4. The trifles can be kept in the refrigerator for up to 2 hours.