Roast leg of lamb with caper and lemon butter crust recipe

Ingredients

• 1.5 kg Maris Piper potatoes, cut into slices
• 0.5 celeriac, peeled and cut into slices
• 1 large onion, sliced
• 4 garlic cloves, crushed
• 3 rosemary sprigs, leaves stripped
• 6 juniper berries
• 1 tbsp capers
• 100 g slightly salted butter, softened
• 1 lemon, zest only
• 2 kg leg of lamb, trimmed
• 450 g fresh lamb gravy, heated