Peel and thinly slice 3 of the oranges, removing all pips and pith. Put the juice from the remaining orange with the sugar, whisky and water in a pan. Heat gently, stirring until the sugar dissolves. Simmer for two minutes. Add the orange slices and raise the heat for 1-2 minutes. Remove from the heat.
Arrange the fruit in a dish and pour any remaining juices from the pan over them. Chill and serve with whipped cream.