Halve and stone the plums.
In a pan, bring the cider vinegar, sugar, allspice, cloves, ginger and cinnamon to the boil.
Once boiled, simmer for 5 minutes and then add the stoned plums.
Cook the plums until just tender, using a skewer to test.
Strain the plums into hot sterilised jars, leaving the syrup in the pan.
Boil the syrup for 5 minutes, then pour over the fruit in the jar and seal it.
Leave the jar for a month before eating.
These pickled plums are gorgeous with cooked ham, roast pork or pate.