Well it is amazing what a different point of view does!
I pulled the board out and found a screw from the gearbox lodged under it. Once that was removed the tank would start

With that sorted I was able to work out where the lead went with a bit of deduction and poke and see what happens trouble shooting. Actually looking at the photo it is obvious when you think about it
It went on the "dot" between the red and black leads next to the bend in the yellow wire.
So I now have a fully functional Tiger again
Now on to the plans for an upgrade

Regards
FlynnOz