Blitz together garlic, spices, anchovy, lemon juice and butter to a rough paste.
Pat the lamb dry and score the skin. Place into a large roasting tin.
Spread the paste over the lamb skin and rub in well. Leave for 30 minutes to marinade
Cover loosely with foil and cook gas Mark 3 160 C for 1 hour. Remove from oven and baste with any juices in the tin.
Mix together the wine and redcurrant jelly with 100ml boiling water, and pour around the lamb. Spread the prunes and quartered red onions around the tin.
Cover the lamb with double foil and seal well.
Return to the oven gas Mark 2 / 150C for approximately 3 hours, basting once.
Remove from the oven and put the lamb onto a hot dish and keep covered. Put the onions and prunes into an ovenproof dish and pop back into the oven.
Remove the fat from the remaining juices which are poured into a pan and reduced for a lovely sauce.
To serve, shred the lamb and serve on a bed of the onion and prunes. Pour over the juices.
To compliment the dish serve with a selection of green vegetables and cauliflower 'mash'.
Notes
Tip: When you have removed the lamb, red onion and prunes from the roasting pan, place several ice cubes into the pan to absorb some of the fat. Remove and discard, taking care not to put the fat down the sink!