Peel the oranges and cut in half horizontally - this makes taking out the pips easier. Remove pips and cut away any white pithy bits. Chop into small chunks.
Put the oranges in a heavy based saucepan, add the juice mixture. Bring to boil then simmer for 1 hour (after 40 minutes you will have to keep a real good eye on it all as it starts to thicken and reduce down

Juice of 4 oranges
Peel from 2 oranges, cut into long thin slices
Juice of 1 large lemon
1 teaspoon bicarbonate of soda
7 oranges
8 ounce granulated sugar