Rub the meat all over with the salt, form into a roll and tie with string. Put into a bowl with cloves, peppercorns, mace, vinegar and sufficient water to just cover it. Leave for 24 hours, turning several times. Drain the meat and place in a large casserole with enough of the pickle to come half way up the joint. Discard cloves and mace, but add the peppercorns to the casserole. Cover and bake in a low oven, 325°F., or Gas Mark 3, for about 3 hours or until meat is tender. Cool the meat in the cooking liquor for about 1 hour, then drain. Put the meat between two boards, place a heavy weight on the top board so that the meat becomes pressed, and leave until quite cold.