Clean the berries well and sort them out. Cut lemon into fine slices. Slit the vanilla pod lengthwise.
Make a syrup from water, sugar and rum, add lemon, vanilla and berries and lightly bubble for 5 minutes.
Immediately following, mold into hot rinsed small jars and screw or clip on the lid, which is also hot rinsed. Twist-off caps are exceptionally suitable for this.
You are sure to find a strong arm to open the lid again when you show him the contents.