Slow-roast shoulder of lamb with anchovy & rosemary

INGREDIENTS

• 4 rosemary sprigs, leaves removed
• 4 garlic cloves , crushed
• 1 tbsp capers , finely chopped
• 3 anchovy fillets in oil, drained and finely chopped
• 2 tbsp olive oil
• 2 whole lemons
• 1½kg shoulder of lamb , on the bone
• 2 red onions , cut into wedges
• small glass white wine