Interesting that 3 airlines that employed him never checked that he had a valid licence. And surely when his LPC checks were done by TRE, a copy goes to the relevant CAA? I am presuming here that it is not just held by the airline? If the CAA got a copy then do they not do a basic check - like put the date of the current LPC on the pilot's record?
I am amazed that all those airlines never bothered to check that a new pilot had the correct documentation!
As for whether it was OK for him to fly because he managed it for 13 years, and some stuff in the ground exams is not relevant, well, surely the job of airline pilot involves honesty, trust and integrity too? What else has might he have faked/ covered up?
And how come he changed jobs so often? Were they on to him?