Put all of the ingredients, except the cherries, into a small pan with 200ml water and bring to the boil, stirring to dissolve the sugar and salt. Pack the cherries into a sterilised 1-litre jar and pour over the pickling liquid. Seal the jar, allow to cool, then chill. Good after a few days, best after a week when the vinegar has mellowed a little. Eat with charcuterie, meat or in salads.