Wash the oranges and steep in boiling water for 2 minutes; peel and reserve the peel of 3 or 4 of them.
Put these peels into 3/4 litres (1 1/3 pints) of boiling water and simmer for 20 minutes; discard the water.
Meanwhile, remove the pips from the oranges and mince, chop, or liquidise the fruit. Remove the pith from the cooked peel and shred finely. Put the Sure-Set, orange pulp, shredded peel and the 250 ml (about 1/2 pint) water in a large saucepan; stir over a low heat until the sugar has dissolved, then bring to the boil and boil vigorously for 4 minutes. (See 'Adding Sure-Set' for details on boiling and timing).
Allow to stand for about 5 minutes, stirring occasionally to distribute the peel.
Pot and cover in the usual way; label and date. (See 'Potting and covering' for details).