This makes a knock-out Sunday roast. Thyme, lime, ginger and cinnamon are classic West Indian flavourings. What’s unusual is grenadine, normally found in cocktails, used to flavour the meat.
Wash the lamb and pat it dry with kitchen paper. Using a small, sharp knife, make incisions all over the meat. Mix all the other ingredients to make a marinade and spread it over the lamb, making sure some goes down into the incisions. Cover with clingfilm and put in the fridge overnight. Turn the lamb over once or twice.