Beat butter, lime zest and sugar together until very pale and fluffy. Add eggs, one at a time and beat completely in to mix between each one. Fold in the flour, add the gin and then bake in a loaf tin for 45 minutes.
Mix icing ingredients together.
When cake is out of oven, poke holes all over and pour over icing.
Leave to cool properly until a crust forms then slice and serve!