Put the whole oranges and lemon juice in a large saucepan or jam/preserve making pan and cover the oranges with the water. You want them to be submerged so you may need to place a plate on top of them, or use smaller pan. Bring to the boil cover and simmer till you can pierce the skin easily with a wooden skewer or a fork (may take up to 2 hours).
Spread half the sugar on a baking tray and warm it in an oven on a very low temperature (125C for 10 or 15 minutes is good).
When the oranges are ready, lift them out of the water and set them aside. When the oranges are cool enough to handle, cut them in half, and carefully scoop out all the flesh, pipes and pits. Put all of that into the saucepan with the cooking liquid, Bring this to the boil and keep it bolig for 6 minutes. Strain the liquid through a sieve into a jug or bowl, pressing gently with a wooden spoon to get as much of the liquid from the pulp as possible. This will be rich in pectin for setting the marmalade.
Put a plate into the fridge on a shelf - not in the freezer section - to use to test the setting point of the jam.
This recipe calls for the marmalade to be made in two batches. To make each batch start by pouring half the cooking liquid into the saucepan. Cut the orange peel into thin slivers and add half to the liquid.
Slice the ginger root thin, tie half of it up in the muslin. Smash the bag or roll over it firmly with the rolling pin to start the ginger juices flowing. Put the bac into the cooking liquid.
Add the sugar and stir over a low heat till the sugar has dissolved. I find this takes only a few minutes if you use caster sugar. Bring the mixture to the boil and let it bubble away for 15 - 20 minutes till the setting point is reached.
To test that the setting point is reached, take the plate out of the fridge, dab a teaspoonful of the marmalade onto it and put it back in the fridge. Wait a minute or two. Take the plate out and tip it on its side. The jam is set if it does not run down the plate. You can also test it by running a finger through the marmalade across the plate. The two sides of the jam should stay apart like the Red Sea parted to let the Israelites through.
If there is scum on the surface of the marmalade in the pan, remove it with a spoon. remove the muslin bag.
Let the marmalade stand for 20 minutes to cool a little and let the peel settle.
Bottle it up in the sterilised jars and seal them.
Repeat from step 4 for the second batch.