Marmalade upside down sponge cake served with a marmalade sauce (J.Salmon)

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Millers Marmalade Pudding
3 tablespoons orange marmalade, 4 oz. self-raising flour, 4 oz. caster sugar, 4 oz. soft margarine, 1 level teaspoon baking powder, 2 medium eggs, Grated rind one orange
Sauce: 4 tablespoons orange marmalade, pint water/orange juice mixed, 2 level teaspoons arrowroot, 2 tablespoons cold water

Grease a 2 pint heatproof pudding basin and place 3 tablespoons marmalade in the base. Put the flour, sugar, margarine, baking powder, eggs and orange rind into a large bowl, mix and beat well for 2-3 minutes until soft and of a smooth consistency. Alternatively use a food processor and mix for 30 seconds. Put this sponge mixture on top of the marmalade in the basin. Cover with a circle of greaseproof paper and then seal with foil. Cover and steam for 2 hours. Prepare the sauce by warming together in a saucepan the marmalade and water/orange juice mixture and simmer for 5 minutes. Blend the arrowroot and cold water to a smooth cream and stir in some of the marmalade mix. Return to the pan and heat, stirring until the sauce thickens and clears. Turn out the pudding onto a warm plate and serve hot with the sauce.