I find it inconceivable that a pilot of his experience had wrongly routed the harness through the ejection handle.
I'm also not able to see on the Mk10b how the safety pin can be inserted and not lock the handle in its proper place- just doesn't work- if the handle is not in housing properly the pin doesn't fit.
Jimgriff, mistakes happen irrespective of how experienced you are, indeed I think it's around 1000 hours is often quoted as the most dangerous time. I knew the chap that LJ101 mentions and the incident - he was hugely experienced. As for the pin - if it can go wrong , it will.