Mary Gwynn's classic Seville orange marmalade

1. Halve the oranges and squeeze the juice, reserving all the pips. Scrape out any white membrane from the skins and tie with the pips in a clean piece of muslin. Tie this to the handle of the pan with cooks’ string to make it easy to remove. Shred the orange peel, either by hand for a finer, more even finish, or in a processor. Place the shredded peel in a large pan or preserving pan with the bag of pips, squeezed orange and lemon juice, and add 2.25 litres cold water.

2. Bring to the boil and simmer gently for a couple of hours (the surface should be moving with small bubbles) until the peel is tender and soft and the liquid reduced by a half. While the peel is cooking, sterilise your jars in a pre-heated oven (160°C, gas mark 3) for 10 minutes, then turn the oven off and leave the jars in it until needed. I also like to warm the sugar in a roasting tin at the same time. It will melt faster when you add it to the juice.

3. Remove the muslin bag and press hard between two plates to squeeze out all the thick juices, which contain the pectin, back into the pan. Add the warmed sugar to the pan and stir until dissolved completely. Bring slowly back to the boil and cook rapidly for 10-30 minutes until a set is reached – it may take longer! If you’re using a sugar thermometer aim for 105˚C.

4. Skim any scum from the surface with a slotted spoon and leave the marmalade to stand for 15 minutes. This lets it set enough to hold the peel. Stir gently, then pot, cover and leave to cool. Label and store in a dark cupboard for up to 1 year.