was missed on pre-flight walk around.
A suggestion, for what it is worth; nothing to do with getting in and out of the doors because if a door is inadvertantly jettisoned it doesn't matter if the door is locked or not.
In 1978 a Bristow 330J lost the pilots door through reasons unknown; probably somebody fiddling;or the pilots nav bag interfering with a jettison lever as the nav bag went with the door. To reduce the chances of it happening again the indicator wire was moved to the inside lever so it was part of the cockpit checks and a frangible plastic cover was placed over it. The wire was touchable around the cover and it was designed so that it fell away from the vertical if broken. There has not been a case of a door falling away since and the doors are frequently used by the pilots during offshore operations. On top of that offshore workers are notorious fiddlers.
At that time there was a fair amount of communication on the technical side between the RAF and Bristows, (it took a long time for Bristows to get their engine alignment tool back from Odiham) so this modification, approved by the CAA, would have been known to the RAF. Whether they followed it up I do not know so it may well have been done.
Just a thought, anyway.