Remove the half lemon rind and pot the jam up into hot jars and place the lids on immediately. (A ladle and jam funnel are useful here).
Before you start:
Put 2 - 3 saucers in the freezer.
Sterilise 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.