Preheat the oven to 180C/350F/gas mark 4
Use a 450g/1 lb loaf tin.
Grease the tin. Line the base with greaseproof paper. Grease the paper. Cream the butter, rind and sugar only until combined. Beat in the sour cream and golden syrup. Transfer to a large bowl. Stir in the pumpkin, then half the sifted dry ingredients and half the orange juice. Stir in the remaining dry ingredients and orange juice. Pour the mixture into the prepared tin. Bake for about 1 hour. Allow to stand for ten minutes before turning on to wire rack to cool. Spread the cold cake with icing.
Carob icing: Sift the icing sugar and carob into a small heatproof bowl. Stir in the butter and enough milk to make a stiff paste. Stir over hot water until the icing is spreadable.
