Preheat the oven to 160C.
Grease and line two 600g loaf tins. (We use a silicone tin so we don’t need to line our tins).
Place the butter and sugar into a large mixing bowl and beat until light and fluffy.
Beat the eggs and then add in to the butter and sugar mixture slowly, until combined. You can still beat it vigorously at this stage; just add the egg a bit at a time. If the mixture looks like it is splitting or curdling, add in a spoonful of flour.
Gently fold in the flour and slowly mix until just about combined.
Add in the zest of the lemons and limes and continue to mix slowly until fully combined. Do not over mix.
Add in the gin and tonic from the cake ingredients and mix steadily until it is combined.
Spoon the mixture evenly across the prepared loaf tins and make a little groove down the centre of the mixture. We weigh our tins to ensure an even split across the tins.
Place in the oven and bake for 30-40 minutes.
The cake should be golden and risen and a skewer inserted into the deepest part of the cake should come out clean.