Mixed fruit marmalade recipe

I MAKE six flavours — Seville Orange, Dark Orange, Lemon & Earl Grey, Lime & Orange, Pink Grapefuit and Orange & Ginger — but I started 35 years ago with this Katie Stewart recipe, which I’ve tweaked. MakES 3-4kg 450g Seville oranges 450g sweet oranges 2 large lemons 1 grapefruit 3½ ltr water 2.7kg granulated sugar SCRUB all the fruit and pick off the discs at the stalk end. Halve the fruit and squeeze out the juice. Quarter the peels and remove excess pith. Slice the peel thinly. Tie the pips and pith loosely in a muslin bag. Put the sliced peel, fruit juices, and muslin bag of pith and pips together in a preserving pan. Add the water. Bring to the boil, cover and simmer gently for 1 ½-2 hours, until peel is tender. Take the pan off the heat. Remove the muslin, squeeze out all the juice by pressing between two dinner plates and discard. Measure the fruit and juice: for every 568ml add 450g of sugar. Stir over a low heat to dissolve sugar. Bring to the boil and boil rapidly for about 15-20 minutes. Take the pan off the heat. Skim, and cool for 15 minutes. Pour into jars, cover and seal while still warm.