In a large bowl add all the wet and dry ingredients together to make the marinade then whisk until well combined
Place the lamb leg onto a roasting tray lined with foil and use a knife to cut several deep slashes into the leg of the lamb – this will ensure that the lamb leg is cooked through and evenly
Add half of the marinade onto one side of the lamb and rub the mixture all over the lamb, including inside the cuts then flip the lamb over and add the remaining mixture and repeat the same process – it is very important that the masala is spread everywhere to ensure maximum flavour then refrigerate for at least 1 hour, for best results try to leave it for 24 hours
Cover the lamb with foil and bake in a preheated oven at 180°C (350°F) gas mark 4 for 2 hours – this will depend on the exact size of leg of lamb that is used, and it is important that you adjust the cooking time as necessary, as a rule the cooking time is approximately 25 mins per 500g of lamb
Remove the foil and add your desired vegetables around the leg of lamb – depending on personal preference the vegetables can be altered but ensure that the vegetables are all approximately equal size to ensure that they are evenly cooked
Drizzle the vegetables with olive oil and add a pinch of salt and black pepper then mix the vegetables to ensure that everything is mixed evenly and well combined
Flip the lamb leg over and increase the oven temperature to 200°C (400°F) gas mark 6 and cook for a further 30 minutes until the vegetables are all roasted and cooked through
Cover with foil and allow the leg of lamb to rest for at least 20 minutes before serving!