How to make Colm O'Gorman's succulent, slow-cooked leg of lamb

Slow-Cooked Hyderabadi Leg of Lamb

One of my favourite things to eat is a slow cooked leg of lamb, where the meat is so tender and soft that you can just pull it apart with a fork. Another is a deep, rich, flavourful curry. 

I adore a great tomato-based curry sauce, one cooked with fragrant, aromatic spices such as cinnamon, clove and cardamom, and that has been allowed to cook slowly so that it develops a richness and complexity of flavour that is just mind-blowingly good.