Gigot de sept heures

I live in an area whose narrow winding roads can ruin the travel calculations of those visiting me for the first time. A couple of friends driving from Saint-Etienne (Loire) said they would be with me in time for lunch. I foolishly decided to cook a roast leg of lamb. Allowing for my guests to be late, I put it in the oven at 12 p.m., so it would be ready for eating at about 1.30 p.m. When they had still not arrived at 1 p.m., I turned the oven very low. Still no sign at 2 p.m., so I turned