Put a saucer or small plate in the fridge.
Remove the skin from the peaches by covering with boiling water, then drain off the water and the skins will slip off easily.
Remove the peach stone (pit) and chop the peaches into small pieces.
Remove the green hulls from the strawberries and cut them into quarters.
Put the fruit in a large saucepan with the water and lemon juice.
Cook for 5 minutes until the fruit softens slightly.
Reduce the heat and add the sugar. Stir until the sugar has fully dissolved.
Bring the jam to a rolling boil and boil for 10 minutes.
Take off the heat and put a teaspoon of the jam onto the cold plate. Return to the fridge for 5 minutes.
Test that the jam is ready to set by pushing your finger across the jam on the saucer or plate. The jam should separate and leave a clear space where your finger has been. It won't wrinkle like higher sugar jam but will definitely leave a clear trail.
If the jam is not set, then bring back to a boil for 5 minutes then repeat the test for set on another cold saucer.
Pot the jam into a sterilised jam jar and seal with a lid.