Pick over the fruit, take any green stalks from the strawberries, take the currants from the strings, stone the cherries and avoid washing if possible, or at most, rinse gently in a colander.
Place in a large jam pan, add the lemon juice and put over a low heat to start the juices running.
When the fruits are heated through, remove from the heat and stir in the sugar until dissolved.
Place back onto the heat, turn it up higher and bring the contents of the pan up to the boil, then reduce to a 'rolling boil'.
When the jam has darkened and thickened slightly, usually after 10mins or so, you can test for a set.
Turn off the heat, and leave to stand for at least 20 mins as if you jar it too hot all of the fruit will rise to the top of the jar.
The jam will keep, in a cool, dark place for several years - there is no need to refrigerate either open or unopened.
Leave to stand undisturbed overnight, delicious with ice-cream or on porridge. Mmmmm!