Hull the strawberries and discard any rotten ones. Set aside about 10 of the smallest berries, and then mash the rest up into a rough pulp. Put into a wide, thick-bottomed pan, add the sugar and the lemon juice, and bring to the boil. Add the remaining strawberries to the pan, and put a saucer in the freezer.
Boil the jam for about 15 minutes, stirring regularly checking the setting point every minute or so during
the last 5 minutes. To do this, take the cold saucer out of the freezer, put a little jam on it, and put it back in to cool for a minute. If it wrinkles when you push it with your finger, then it’s done. Strawberry jam is unlikely to set very solid though, so don’t expect the same results as you would with a marmalade.
Take off the heat and skim off the pink scum. Pour into sterilised jars and cover with a disc of waxed paper, seal and store