Increase heat and bring to a rolling boil then time for 5 minutes, stirring occasionally with a wooden spoon.
Run your finger through the drop and if it forms a crinkle and is tacky it’s ready.
Skim any scum off the top with a spoon and add a small knob of butter to disperse any remaining scum if you wish.
Ladle into a small sterilised jar (yield 210 ml) (see notes below) and seal with lid immediately. You can alternatively use a sterilised glass with a wax paper disc, leave to cool and then put cellophane on with a rubber band.
Before you start:
Put 2 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.