The Teeside incident was indeed an S58ET and I seem to remember that the unusual attitude was attributed to jack icing. The 58 on the Teeside contract was a bit different because Lawrence B had got his payload sums wrong and part of the resultant aircraft lightening programme was the removal of the bifilars. The 58T was normally smoother than the Wessex, but was much rougher after they were removed.
I'm getting a bit more ancient now and can't remember the name of the pilot, although I can remember his face clearly - a former crab Squadron Leader I seem to remember
