He does not know (yet) what caused the double failure., the BEA is looking into it.
I shall certainly be interested in hearing the BEA findings.
We had a PA-30-160 similarly suffer a double engine failure in the early 1980s en-route Southend to Doncaster. Luckily it was daytime VMC and our Chief Pilot was flying the aircraft. He issued a Mayday call and headed for RAF Barkston Heath while trying to restart the engines. While on finals for a dead-stick landing one engine did restart but he continued with the landing as being the wisest choice. RAF Cranwell sent over a vehicle to collect the two pax and took them to the nearest rail station to continue their journey. Our Chief Engineer flew up to examine the aircraft and despite extensive checks and ground runs could find no fault so flew back with the aircraft to Southend.
So we never found the cause of the incident and nothing of the like ever happened again. There was a slightly amusing aspect to this in that I was in a meeting with a client who wanted to discuss a new contract and an Ops Officer rushed in to say that " ***** has just declared a Mayday." I told him I would come through in a moment and the client looked at me and said "Mayday? That's serious isn't it?" to which I replied "It can be. Please excuse me for a few minutes." We got the new contract.