Put 2 - 3 saucers in the freezer before you start.
Sterilise 2 x 450 ml jars by washing in hot soapy water (or take straight from dishwasher), fill with boiling water, empty and then place in oven for 20 minutes at 140°C where you leave them until the jam is ready. Washed lids should be sterilised with boiling water and then left to drain.