Using a hand blender or food processor, blend all the marinade ingredients together to form a puree.
Place the lamb cubes into a zip-lock plastic bag and then pour in the marinade. Seal the bag and toss the meat around to ensure it's all coated. Leave in the fridge for 24 hours. If you're in a hurry - 4 hours is the minimum I would leave it. If you haven't got 4 hours... make this when you HAVE got 4 hours. :)
Once the meat has marinated, thread around 6 pieces of meat onto skewers (if you're using wooden skewers, you should soak these in water the same time you put the meat into marinade. it'll stop them disintegrating on the grill). I use metal skewers, they're much easier than wooden.
Heat your BBQ grill until hot - you can use coals or gas BBQ - you'll get good results with both.
Grill the meat for about 10-12 minuets, turning once or twice. I also like to brush a little ghee over them during cooking to keep them moist and to create a bit of smoke action for extra flavour - this is optional.
You can also cook these under a hot oven grill for around the same time, turning occasionally.