Right oh Richard.
You make the Sauce if you wish and I will slow cook the lamb. I have not got a thick based cooking vessel so the answer to this is I will use a Tin but raise it up above the embers
the higher it is raised the slower it will cook.

Has I explained to folk at Pigs Ear if you hold you hand low over a flame its bloody hot and if you keep it there it will burn/cook your hand.

If you raise your hand over the same flame it will cook and if you raise it over the flame so its a bearable heat it will not burn your hand for some time but it will get hot and it will cook it after a while .Slowly
Its all about height and heat.
                                                                     
Lamb cooking

Lamb is a some what bland meat .
It also smells awful during cooking.
But tastes lovely.

I will cook the Lamb on the Thursday morn should take a slow 4 hours I will steam it
and then brown it off .
                                              Optional
I suggest you then add your Sauce and we flash heat it.

Basically that means fire bomb the joint . one runs away to excape licking flames and then returns when the flames have died down. This process well it kinda caramelizes the sauce.
regards Pierre