To start, weigh the meat to calculate cooking time. Roast gammon cooking time is generally 20 minutes per 450g, plus an added 20 minutes.
Put the meat in a large pan, cover with cold water and bring to the boil, adding any flavourings you wish (cinnamon, bay, peppercorns, coriander seeds and onion all work well).
Boil for half the calculated cooking time, periodically skimming and discarding any white froth that rises to the surface.
Drain, reserving the stock if you like, and leave to cool a little. Remove the top layer of skin, leaving a thin layer of fat around the meat.