Seville Orange, Grapefruit & Thyme Marmalade

1. Remove the green buttons (where the stems were attached) from the oranges, lemons and grapefruits and pop them into a large pan. Pour over 2½ ltr cold water and cover with a lid. Bring the pan to the boil, then simmer over a medium heat for 2 hrs. After 2 hrs, turn off the heat and allow to cool for 3-4 hrs.

2. Sterilise your jam or preserving jars – you should make around 2 ltr marmalade. You can sterilise the jars by putting them through a dishwasher cycle, or washing them in hot, soapy water, rinsing them and then drying them in an oven set to 100°C/Fan 80°C/Gas ½. Put 3-4 side plates into the freezer to chill.

3. Use a slotted spoon to scoop the citrus fruit out of the pan onto a chopping board (keep the water in the pan). Line a large bowl with a large square of muslin. Halve the oranges, lemons and grapefruit and use a spoon to scoop the flesh, pips and membranes into the muslin. Tie the muslin into a tight bag, securing with string if needed. Gently squeeze the muslin bag over the pan, scraping any sticky liquid that comes out of the bag into the pan. This is the pectin, which will help the marmalade set. Pop the bag into the pan.

4. Slice the orange, lemon and grapefruit peel to your preferred thickness and slide it into the pan. Tip in the sugar. Pick the thyme leaves off their woody sprigs and add them to the pan.

5. Warm the pan over a medium heat for 5-10 mins, stirring occasionally, till all the sugar has dissolved. Turn the heat up and bring the pan to the boil – keep your eye on it as the marmalade will froth and start to boil up. As soon as this happens, turn the heat down to stop it overboiling.

6. Keep the marmalade at a rolling boil until it reaches 105°C. If you don't have a sugar thermometer, boil for 20 mins, then take it off the heat. Pour a spoonful of marmalade onto a chilled side plate, leave it for 1 min, then press it with your finger. If it has set and wrinkles when you press it, it's ready. If not, put the marmalade back on a medium heat and boil for a further 5 mins. Repeat the wrinkle test. The marmalade should be ready within 20-35 mins.

7. Use a tablespoon to skim any scum off the top of the marmalade. Ladle it into the sterilised jars, seal and label. The marmalade will keep for up to 1 year in the sealed jars.