Marguerite Patten, Cookery in Colour, p1001
1 grapefruit
1 sweet orange
1 lemon
2¼ pints water
Wash fruit thoroughly and put into a pan with the water. Cover and simmer slowly for about 1½ hours (or until a blunt wooden skewer will pierce the skin of the fruit easily).
Remove fruit from water, allow to cool, and cut into small pieces.
Put the pips into the water and boil vigorously for 10 mins (to extract the pectin), then remove.
Place the cut-up fruit into the water, and bring to the boil.
Stir in the sugar (warmed for a few minutes in the oven).
Continue stirring until sugar is dissolved, then bring to the boil, and boil rapidly for approx 15 mins, until the setting point is reached.
Allow to cool slightly, stirring occasionally to prevent fruit from rising. Ladle into warmed jars and cover.