What weight gammon do I need?

[Jungfraujoch]

Doing a slow cooked gammon for Xmas - need about 15-20 servings. Can someone advise what weight please? Thanks.

My advice would be just don't do gammon. It's extremely salty, doesn't do good left overs and it always (always) feels like 1972.
If you want to avoid turkey do a leg of lamb, a beef wellington (yum), or a pair of ducks.

Sorry Gonzo I disagree! We have turkey plus a little gammon on Xmas day and then leftovers with pickles Boxing Day. Very traditional in this house!