Heat your oven to 220°C/200°C/Gas 7. Unwrap your lamb. Pat it dry. Let it get to room temperature.
Peel and finely chop a clove of garlic. Halve the rest of the garlic bulb. Wrap in foil and set aside.
Place the chopped garlic clove in a pestle and mortar or small bowl. Add the coriander seeds. Grate in the zest from both oranges.
Crush with a pestle or the bottom of a glass to mix everything together and soften the coriander seeds. Stir in a good pinch of salt and pepper.
Massage all but 1 tsp of the mix into your lamb. Get right into the grooves of the meat, where it’s
been rolled. Set the lamb in a roasting dish. Halve one of your oranges. Add it to the tin. Pop in the foil wrapped garlic bulb.
Roast the lamb in the oven for 40 mins. Your lamb should be cooked medium after this time. If you prefer
it less pink, cook for a further 10-15 mins.
Remove the lamb from the tin and transfer the meat to a cutting board. Rest for at least 30 mins before carving. The garlic should be soft. If not cook for a little longer till it is.
While the lamb is resting make your zesty gravy. Juice the remaining orange halves. Squeeze the roasted garlic cloves from their skins and mash to a paste with the back of your knife. Warm the pan juices with the orange juice, a glass of white wine and a little honey. Add the squashed garlic and some seasoning.
Reduce the mix down to your liking for about 15 mins, tasting and tweaking the flavours as you go. Serve drizzled over the zesty lamb.