Roast Leg of Lamb with Shrewsbury Sauce

First of all, place the meat in the roasting tin, tucking the slices of onion beneath it.

Season the surface with salt and freshly milled black pepper, then place it, uncovered, in the pre-heated oven on the middle shelf. Roast for 30 minutes per lb (450 g) – for a 5lb (2.25 kg) leg this will be 2½ hours. Make sure that you baste the lamb at least 3 times while it is cooking, as this will help keep it juicy and succulent.

If you like to serve your lamb quite pink, give it 30 minutes less cooking time. To tell if the lamb is cooked to your liking, insert a skewer into the centre, remove it, then press the flat of the skewer against the meat: as the juice runs out, you will see to what degree the meat is cooked – the pinker the juice, the rarer the meat.

When it is cooked as you like it, remove it to a carving board and keep it in a warm place to rest for 30 minutes. Now, to make the sauce, spoon off any surplus fat from the roasting tin, tipping it to one side and allowing the fat to separate from the juices; you need to leave about 2 tablespoons of fat behind. Now place the tin over a direct heat turned to low and stir in the flour and mustard powder until you have a smooth paste that has soaked up all the fat and juices. Next, add the wine, a little at a time, mixing with a wooden spoon after each addition. Halfway through, switch from the spoon to a whisk and continue to whisk until all the wine has been incorporated. Now simply add the redcurrant jelly, Worcestershire sauce, lemon juice and seasoning, then whisk again until the jelly has dissolved. Now turn the heat to its lowest setting and let the sauce gently bubble and reduce for about 15 minutes, then pour it into a warm serving jug. Carve the lamb, garnish with the rosemary, pour a little of the sauce over and hand the rest round separately.