Seville oranges are so-called after the city in southern Spain where they are extensively grown. Seville oranges are good for preserve making as they have a high level of pectin, which makes a good set.

Seville oranges are used because they are bitter and when combined with sugar, the predominant flavour is that of the oranges, with a sharp tangy taste.

The Seville orange season is short, from December to February, so its best to make enough marmalade to last all year. But if you have the space in your freezer, Seville oranges can be frozen.