My Mom had trouble boiling water, she was not much of a cook. But with Tea, Lamb, white gravy, and white beans Mom could really do things right.
Firstly, be sure you get your mutton from a younger ewe. All lamb has an odor but it is more powerful and longer lasting wtih the older animals. More pronounced they call it. My Dad could smell the difference....
Do not trim the fat.
Do not remove the bone prior to cooking.
I have eaten it rare but deep pink, yeah, that's good, please do not cook well done it gets tough and the flavor departs.
When baking for Sunday Dinner surround the leg with potatos, carrots, celery, onions.