Combine the water, lemon juice, salt, garlic, pepper, bay leaves, parsley and chives. Place the ham in the marinade and marinate 8 hours or overnight in the fridge, turning occasionally. Reserve the marinade.
Place the ham in a roasting tin and spread the butter over it. Cover with aluminium foil with the shiny side towards the meat. Bake 1 hour, then remove the foil.
Bake another 40-50 minutes until browned. During this part baste occasionally with the marinade.
Set the ham aside on a platter. Place the roasting tin on a burner, add the flour, orange juice and wine and stir, scraping up the burned bits, to make a gravy. Strain the gravy and pour into a gravy boat. Serve with the ham.