How has this Progressed ?
It clearly seems to refit the others and then try the dud un...
In OTHER situations where you can access the bolt head, i have found it
VERY HELPFUL to file down some/all the edges and then fit a
smaller socket/spanner HEAT with blowtorch and remove (for any1 reading)
Bu this is very limites access, and so drilling with the above Excellent guide
By Tabetha, is the Way Forward here...
Let us know how you get on...
Paul