Lightly scrub the fruit then place it in the preserving pan, add 5 pints (3 litres) of water and bring it all up to a gentle simmer. Cover with double foil and simmer for 3 hours.

Remove the preserving pan from the heat and allow everything to cool enough to handle. Lift the fruit out of the liquid into a colander.

Cut the oranges in half and scoop out all the inside flesh and pips into a medium-sized saucepan. Do the same with the lemons but discard the peel.

Add 1 pint (570 ml) of the poaching liquid to the fruit pulp, then simmer for 10 minutes.

Strain the contents of the saucepan through a nylon sieve lined with gauze and leave to cool and drip through.

Cut the orange peel into chunky strips and add them back into the preserving pan.

Gather up the corners of the muslin and squeeze all of the pectin-rich juices into the preserving pan. Discard the pithy membranes.

Leave the mixture overnight, loosely covered with a clean teacloth.

The following day, warm the sugar in a roasting tin in a warm oven for 10 minutes.

Place the preserving pan over gentle heat and add the warmed sugar, stirring until fully dissolved.

Once dissolved, increase the heat and let the marmalade bubble gently for 3-4 hours until it darkens.

To test for a set, spoon a teaspoonful of marmalade onto a chilled plate and check for a crinkly skin.

When set, cool for 30 minutes before ladling into jars that have been washed and warmed. Seal with waxed discs.