Herb-crusted lamb with gravy

3 kg leg of lamb

3 small garlic cloves, sliced

2 onions, cut into chunks

1 carrot, cut into chunks

2 tbsp Dijon mustard

For the crust

175g white breadcrumbs (a few days old is best)

Small bunch parsley, finely chopped

Small bunch mint, finely chopped

5 rosemary sprigs, leaves finely chopped

2 large garlic cloves, crushed

3½ tbsp olive oil

For the gravy

2 tbsp plain flour

400 ml red wine

1ltr lamb or beef stock

1-2 tsp Dijon mustard

Knob of butter