Slow cooking in the oven is an absolute godsend for the harrassed host. In the place of precise timings and last-minute stress, this method means that the work is all done hours in advance (freeing up the time to be stressed about another course instead!). By the end of this past Christmas weekend - which, in practice turned into three consecutive dinner parties, interspersed with two consecutive lunch parties (a lot of fun, but....well, you know) - to be able to turn to this method for the main course for dinner on Boxing Day was an enormous help. Painless, and entirely reliable. (One thing to remember, though, with this method is not to rely on your oven controls to tell you what temperature the oven has reached, but to put an oven thermometer in the oven alongside the meat and to take your readings from that - something I've learned from bitter experience!)
For one Lamb Loin (enough for eight servings):
1. Remove the joint from the refrigerator for long enough for it to reach room temperature, (about 3 hours before you want to start cooking). Then , using a blow torch, flame the joint all over to kill any surface bacteria. Season and tie the joint neatly.
2. Pre-heat the oven to either 60°C (for medium, or pink lamb at the end of cooking) or to 65°C (if you prefer your lamb more cooked). Place the lamb in a dish with a piece of foil loosely laid over the meat, and cook for 3½ hours. (For those that like lamb really 'well done', set the temperature at 70°C.) If your oven has multiple settings, make sure to use the setting without the fan, as otherwise you risk the joint drying out. Once the joint has heated through, remove it from the oven and it can be 'held' until needed
3. 30 mins before serving, heat the oven to maximum. When the oven has reached maximum temperature, set the joint on a wire rack and roast until the outside is well browned, 10 - 15 mins. (If you have a gas grill or similar you can use this to brown the joint, instead).
4. Keep the joint warm while you have your first course then carve, season and serve on hot plates with a little hot sauce of your choice (I normally make a reduction of stock and red wine).