Most hams these days should not need pre-soaking as they are not as heavily salted, but if buying from a butcher just ask.
In addition to this taste the cooking liquor about half way through cooking and if it is overly salty pour half away and add more water.
Place your ham in a large saucepan with a quartered onion (skin on), a couple of roughly chopped carrots, a couple of chopped sticks of celery, half a chopped leek (green end), a few bay leaves and half a dozen pepper corns.
You can use other stock veg if you have things that need using up or trimmings.
Cover with water and bring to the boil. Reduce the heat to a rolling simmer and cook for half an hour per half kilo.
Twenty minutes before the ham is ready melt a good knob of butter in a sucepan and remove from the heat.
Stir in a couple of teaspoons of plain flower and add a dash of milk.
Return to the heat and bring to a simmer, stiring constantly, while adding a combination of more milk and cooking liquor from the ham until you have the consistency of a sauce.
Add lots of finely chopped parsley and keep warm until the ham is cooked.
Remove the ham from the cooking liquor and leave to drain for a few mins.
Slice and serve with the parsley sauce and seasonal veg or veg lightly cooked in the ham liquor.
Reserve the stock for soup.