Put a small plate in the freezer
Blitz the fruit to desired smoothness in the pot you will use to cook the jam
Put the pot on a medium-high heat and add the sugar
Once the sugar is mixed in, add the lemon juice and stir and then add the vanilla
Bring just to the boil and move to a low heat.
Cook for 30 minutes.
Take the plate out the freezer and put a spoonfull of jam on.
Make a line through the jam on the plate with your finger. If the jam flows in to close the gap cook for longer, if it stays solid your jam is ready.
Skim the scum off the top (rather do this once at the end as you will lose less yummy jam)
Pour into sterelised jars and allow to cool.