Beat the butter and sugar with an electric mixer for 5 minutes (or with a wooden spoon) until light and fluffy.Beat in the orange zest, then beat in the eggs one at a time. Sift over and gently fold in the flour, a pinch of salt and the chocolate chips.

Heat the oven to 170°C/fan150°C/gas 3. Grease an loaf tin and line with baking paper,

Spoon the mixture into the prepared loaf tin and level the top.

Bake for 45 minutes - 1 hour until nicely browned and until a skewer pushed into the centre comes out clean. (Baking timing may be vary according to the oven in use)

Leave in the tin for 10 minutes, then remove the paper and turn out onto a wire rack. Peel off the baking paper. Leave to cool before slicing.