Method
Preheat an oven to 180°C, gas mark 4. Line a loaf tin with baking parchment. Hull and lightly crush the fruits. Sift the flour into a mixing bowl. Add the soft brown sugar. In a small bowl whisk the eggs and add the buttermilk. Zest and juice the lemon. Melt the butter. Add the egg mixture, lemon zest and melted butter to the flour and sugar, combine. Fold in the blueberries, raspberries and strawberries. Tip into the loaf tin, sprinkle over the castor sugar and bake for 45-50 minutes until the well risen and a golden colour. Rest in the tin for 10 minutes. Remove. Allow to cool on a wire rack. Combining the icing sugar with lemon juice to make a smooth icing. Drizzle over the cake. Use as required.