Remove the zest from an orange and a lemon and cut into fine strips; cook 1 generous tablespoon of the zest very gently in 2 dl (7 fl oz, 3/4 cup) port for about 20 minutes.
Remove the zest and add to the port 2 tablespoons (3 tablespoons) redcurrant jelly, then a pinch of cinnamon and a pinch of cayenne.
Mix, bring to the boil, add the juice of the orange and lemon, then strain.