1. Prick the walnuts all over with a carpet needle. Place the nuts in a ceramic bowl, dissolve half the salt in half the water and pour over the walnuts. Cover and leave for 5 days in a cool place, stirring twice a day to ensure even brining.

2. Drain the walnuts, mix the remaining salt and water, pour over the brine and leave for another five days, stirring twice a day as before. Drain, spread out in a single layer on a flat dish and leave to dry in the sun until they are black.

3. Crush the peppercorns and allspice berries and simmer the vinegar with the spices for 20 minutes. Allow to cool and strain. Pack the walnuts into sterilised, wide-necked jars, filling them no more than three-quarters full, and pour in the spiced vinegar. Cover and leave in a cool place for 6 weeks before using.