When you are ready to make your marmalade, transfer the marmalade mixture to a large saucepan and on a medium heat simmer gently until the orange peel is soft and the water content is reduced by about half. This could take 45-60 minutes, depending on the thickness of the oranges peel)
Test (and taste) the peel to make sure it's soft and cooked through. The orange and lime peel will look see-through and more opaque than before.
When the peel is soft, check that you have about 500ml of water/liquid left.
Squeeze the muslin bag with orange & lime pips and pith and discard.
Add the orange and lime juice saved from the first stage of your marmalade making and top it up to 500 ml. You can use water or other (shop bought) orange juice.
Add sugar and let it dissolve properly. Check on the back of a soup spoon that all the sugar crystals have dissolved before you move to the next step.
Once the sugar has dissolved, bring the marmalade to boil and boil for about 10-15 minutes or until you reach the setting point.
Check your setting point using a cold plate and a spoonful of the marmalade.
Once you are satisfied that your marmalade will reach the setting point, take it from the heat and leave it to stand for about 5 minutes. This will help to distribute the orange peel more evenly once potted.
Divide between 3-4 jam jars, seal and let to cool down properly before storing away in a dark, cold place. Use within 12 months (or two years maximum).