Give your oranges and grapefruit a good scrub and peel the skin off your ginger.
With a serrated knife, very finely slice the fruit. I like to cut the fruit in half, slice it finely and then cut those pieces into smaller pieces. You can slice it as you like.
Slice and then dice the ginger.
Add your oranges, grapefruit and ginger to a large enough pot and cover it with water and sugar. Put a lid (or plastic wrap) on the pot and leave it on a counter overnight to absorb the sugar.
The next day, place the pot on the stove and bring it to a boil. Once the mixture is boiling slightly, reduce the heat and let your marmalade simmer for about an hour. Resist the urge to disturb the fruit while it cooks.
While the marmalade cooks, sterilise your honey jars and place a dish in the fridge to cool. Once an hour or so has passed, you can test the consistency of your syrup by placing a small amount on the cold plate. The thicker the mixture, the closer it is to being ready.
When the marmalade has cooked and has a nice consistency, bottle it while it is hot. This will help the bottles to seal.