Pre -heat oven to 180ºc, fan 160 ºc, gas 4.
Grease and line a 2lb loaf tin, cream the butter and sugar together. Gradually add the beaten eggs, adding a spoonful of flour with each addition to stop the mix from curdling. Add the rest of the flour and stir well. Fold in the chopped mango.
Bake for 45-50 minutes, until a thin skewer inserted into the centre of the cake comes out clean. Leave in the tin for 15 minutes and then turn over onto a wire rack.
For the icing, beat the icing sugar and unsalted butter together until it is pale and creamy. Add the lime zest.