I usually like my lamb well done, and that's great for shoulder, but it's not really a great way to cook leg in my opinion. Leg doesn't have the fat content of the shoulder, so it's all too easy to create something dry and not so palatable when roasting a leg for a long time - generally speaking you're better off aiming for something pinker. That was my plan this Sunday, so after consulting the usual battery of cookbooks I decided on half an hour hot (220ºC) and then 15 mins per pound cool (160ºC) for my 5 lb leg of (very well hung) Lamb. Nothing too special about this one - just coated in a very light layer of olive oil, well seasoned with salt & pepper and resting on 3 good sprigs of rosemary and a few cloves of garlic.
The meat out of the wrapping
The meat ready for the oven
For the potatoes I reckon the secret it to get them really dry before they go in the hot oil/fat. I always parboil when I'm doing 'proper' roast potatoes, and do this well ahead of when they need to go in so that they can steam and dry out. A good shake in the colander is enough to give you a rough texture to pick up the fat - I normally use beef dripping, but didn't have any today, so used some of the fat from the lamb pan which was lightly flavoured with the rosemary and garlic from there. Ten minutes in the hot oven first gets the oil good and hot, then in go the potatoes (carefully!), a few turns to cover and then in for about an hour, depending how well browned you like them.
Parboiling potatoes
Making gravy
Preparing the plates
Finished dish
P.S. These videos were all shot with my new Nexus One phone from Google - not bad I think, better quality than my previous phone that's for sure.