2 x Seville (bitter) oranges
1 x lemon
1 x Valencia (large, sweet) orange
Put fruit in a pan of water and boil for one hour
Leave to cool
Cut fruit in half and remove pips
Put water and fruit in food processor and turn to slurry
Transfer to jam making pan
Start to boil
Add sugar to taste
Boil until set achieved
The pips can be put in a glass with a little water overnight and the resulting pectin added to the fruit the next day.
I determine set by taking a small sample, putting it on a saucer, allowing to cool and then seeing if when the saucer is vertical it runs.