Place the fruit (still whole) in a large pan with the water.
Weigh them down with a heat proof plate or pan lid so that they are fully submerged.
Bring the water to the boil, cover the pan and simmer for 2 hours or until the oranges and clementines are very soft.
Take the oranges and clementines out of the plan and place them on to a cooling rack. (Do not throw away the water at this stage).
Once the fruits are cool enough to touch, cut them in half and remove any pips, fibrous bit of membrane and any bitter pith.
Retain the juice in a jug for later.
Add the pith back into the pan along with the cooking liquid and simmer uncovered for 15 minutes.
Meanwhile cut the peel into thin strips (as thin as you like).
Strain the cooking liquid into a heavy bottomed preserving pan or sauce pan making sure to remove all of the pith from the cooking liquid.
Squeeze the pitch to make sure you've got as much pectin out as possible (this will help it set).
There should be roughly 1 litres of water left, top it up with water as necessary then add the whisky.
Add the sliced peel and juice to the pan along with the sugars.
Stir over a medium heat until the sugar has dissolved.
Bring to the boil and boil rapidly for about 8 - 15 minutes for the perfect set.
To test for the correct set, turn the heat off and spoon a little of the marmalade onto a cold plate (make it cold quickly by popping in the freezer). Leave the marmalade for a few minutes to see if it sets.
If not, boil the marmalade for a few more minutes and test again until it has a jelly.
Using a spoon, skim off any scum that appears on the surface.
Leave the marmalade to cool for 15 minutes while steralising your jars.
To steralise your jars, either by put them in the dishwasher or washing them with soapy water and leave them to dry in the oven, or use food safe steralising powder.
Once the marmalade has cooled slightly pour into your jars.
Screw on the lids tightly and allow to cool, they will "pop" when they are sealed air tight.