Pound together in a mortar the anchovies and rosemary leaves, adding a little of the anchovy oil if necessary, to form a thick paste. Cut small slits in the lamb and insert slivers of the garlic.
Score the lamb with a sharp knife and spread the paste over thickly. Roast uncovered, for 20 to 25 minutes per lb. Then leave to rest for a while in a warm place.
Strain most of the fat from the roasting tray. De-glaze it with a glass of wine, bubble in a drop of stock till it reduces, whisk in a knob of butter and strain it into a sauce boat.
© 1988 Keith Floyd estate. All rights reserved.