Wash strawberries and peaches. Remove the green from the strawberries, cut the peaches into 4 pieces along the stone. Cut the strawberries and peaches into very small pieces. Remove the peel from the bananas and cut into very small pieces.
Put everything in a large saucepan and chop up with the hand blender. Depending on your taste, with or without pieces of fruit.
Squeeze the lemon, add the juice, add the vanilla and preserving sugar and continue stirring. Let everything rest for 2-3 hours.
Then bring to the boil and cook for about 4 minutes. Put a gel sample on a plate. When this has gelled, pour the jam immediately into the prepared jars, close and let them cool. If the sample does not gel, add the preserving sugar and boil. For me, 3/4 of a pack of preserving sugar 2: 1 was enough.