It's not a new idea and I can't claim credit for it ~ but thanks for the kind words anyway.
It was a bit of a play to see whether it was possible

. One and a half (ish) fills of an old but 'legit' civvy trangia burner was more than enough to bake the pie, heat the veg (tinned on this occasion ~ fresh would take longer) boil water for a decent sized brew and for washing up

.
I'd say that it could have been done on one filling ~ lots of time, heat and fuel were lost due to fettling and adjusting.
The one thing I definately need to look at improving is the method of raising the item being baked. This pie was sitting on three similar sized stones and, due to the amount of extra space, the pie tin slid when I moved the mess tin

and I gained extra losses on the heat, time and fuel use opening the mess tin to reposition the pie tin


. I think a small rack would be a better option ~ and it would also allow the possibility of baking multiple items

.
Cooking time for the pie will be comparable with what it would be at home