Beat the butter with the first lot of oregano/marjoram and the mustard. Trim lamb and cut slits 2 cm deep over the surface. : Spread the butter all over the meat, and push it into the slits (I like to do this a couple of hours before cooking). Place on a wire rack that will fit over a roasting pan. : Halve, core and deseed the red pepper then cut into chunks. Cut the aubergines into similar sized chunks. Pour the olive oil into the roasting tin and stir into the vegetables. (I used half an onion as well, and it worked well). : Place the wire rack and lamb on top and roast at 200C (400F) mark 6 for 20 mins per pound plus 20 mins for medium cooked lamb. Stir the vegetables twice during cooking. : Turn off the oven and transfer the meat to a serving dish and leave in the turned off oven for 15 mins. If necessary, brown vegetables over a high heat, stirring all the time. Spoon the vegetables around the lamb. Stir in the oregano and serve immediately.