Compost Heap Marmalade

The recipe was discovered in a British cookbook.  We first made it with citrus fruits left over from other marmalades.  Now we pick a day in February, the height of citrus season, and  buy some of each variety of citrus fruit available on that day.  We leave out the more bitter peel such as lime or grapefruit and as a result, a very fresh citrus flavour dominates.  It is thick with fruit and slightly different every year.