Wash and dry the oranges.
Remove the orange zest using a citrus peeler or paring knife, making sure to remove as much of the white pith as possible as this is very bitter.
Chop the zest into thin 3cm strips, and add to a medium sized pot, with sugar and water. Set aside.
Cut both ends and the thick white pith from around the orange flesh and discard.
While working over a large bowl to catch the juices, cut the segments out of the oranges.
Once all the fruit segments have been separated, squeeze the remaining juice from the membranes and place these, along with any seeds, on a cheese cloth and tie this into a parcel. *The membranes and seeds contain pectin, a crucial ingredient which aids in setting the marmalade.
Add the orange segments, juice and parcel to the pot, and bring the mixture to the boil while stirring to dissolve the sugar.
Lower the heat to a simmer and simmer for 2 hours until the peel is tender and breaks apart when pulled.
Remove the parcel, squeezing it firmly against the side of the pot to extract as much pectin as possible.
Bring the marmalade back to a rolling boil for 15 minutes to reach the setting-point. *The marmalade is done when the mixture is thick and glossy.
Test your marmalade on the back of a cooled metal spoon. After a minute, a slight skin should form, meaning it is done.
Remove the marmalade from the heat and leave to cool for several minutes.
Stir to incorporate the peels evenly into the mixture, and transfer into warm sterilised glass jars, leaving 3mm of space at the top of each jar. Close with the lids, and store in a cool, dark place.
The orange marmalade will keep up to 1 year if stored properly.
Refrigerate after opening, and use within 4 weeks.