Tips for cooking a whole lamb in a fire pit? A while ago we tried to cook a whole lamb in a fire pit.  Basically we dug a pit about 2-2.5 feet deep, lined it with rocks to try and retain the heat, made a large fire in it, and started to drink.  Then when the fire had died down a bit we lined the fire with some damp straw, put in the hessian wrapped lamb, put more damp straw on top then covered the whole thing with earth and left for 24 hours.

When we dug it up, the lamb was done beautifully on the fire side, but raw on the top.  

What might we have done wrong, apart from getting drunk whilst the fire was burning?  Has anyone done this before and what are the things that we should bear in mind if we do it again?
In the past when I've cooked in the ground I put rocks into the fire. Don't really know what sort of rocks, but I've been involved in sessions that use bricks. 

Point is that you needs some way to "envelope" the heat around the thing you are cooking so what we did was put the rocks into the fire to heat them up.

Carefully remove the rocks before putting the lamb in and then put the hot rocks on top of the hessian covered meat before putting the dirt back on top.

Let it sit for a while and you should get a much more even result