1. Place the cake mix, tonic water, lemon juice and oil into a bowl.
2. Mix together to form a smooth batter.
3. Add the lemon zest and mix again.
4. Pour into a well greased or pre-lined (2lb) loaf tin.
5. Bake in a lower half of a preheated oven 170°C (340°F, Gas Mark 3-4) for approximately 55-60 minutes.
6. Remove from tin and place on a wire tray.
7. Prod the warm cake all over with a fork or skewer.
8. Taking the 2 heaped tablespoons of icing sugar, tip out the sherbet from the Sherbet Fountain and add the 70mls of Gin.
9. Mixed together and brush or pour the Gin drizzle all over the cake.
10. Decorate with slices of lemon & the sprig of mint.