Stone the fruit and poach in the water for about 30 minutes very gently to soften the skins.
Add the sugar and vanilla and stir until dissolved. Boil to setting point and pop into sterilised jars – keep an eye on it as it tends to boil over. To test for setting point before you start making the jam place a few saucers in the freezer. When you think the jam is ready, pour a few drops onto the saucer and leave for a minute or so. Push the jam with your nail – if it crinkles/wrinkles, it’s ready.