Preheat the oven to 210ºC/425ºF/Gas Mark 7. Season the outside of the lamb with salt and pepper then rub with oil. Heat a small frying pan with a metal handle or a roasting tin on the hob, add the lamb and fry for 4-5 minutes, turning until browned. Transfer to the oven and roast for 25-30 minutes for medium or 35 minutes for well done.
Meanwhile, add the potatoes to a saucepan of boiling water and simmer for 15 minutes.
To make the sauce, add the star anise, orange and lemon rind and juice, the wine, sugar and 3 tablespoons of water to a medium sized saucepan, heat gently for 5 minutes, stirring from time to time.
Mix the cornflour with the remaining 1 tablespoon water then add to the sauce with the cherries and cook gently for 5 minutes, stirring frequently until the cherries are just softened, the sauce has thickened and is a deep cherry red.
Wrap the lamb in foil and leave to stand for 5 minutes. Drain and coarsely crush the potatoes with a fork then mix in the crème fraiche, chopped mint and salt and pepper. Spoon the potatoes on to serving plates, thinly slice the lamb and arrange on top, add any meat juices to the sauce and reheat if needed then spoon around the lamb. Serve with steamed green beans if liked.
For top tips on protecting you and your family when preparing raw meat and poultry, visit Food Safety in the Home and view the full Food safety at home video.