As an observer, it does seem that there are many links in the chain, outside the pilot's direct control, but for which he is ultimately responsible. Would this be fair to say? It would be interesting to hear from line pilots on this. Does BA, for instance, require dual independent checks on cowl doors?
As a line pilot of a similar sized aircraft carrying out similar flights ( B737) I can say that there are many many things that the pilots are " ultimately responsible" for that are fairly well out of their control.
That the latches on the engine cowls have been closed is one example ( if they were still being worked on when the walk around was conducted).
That the pitot tube has been re connected after maintenance on the system is another example ( recently had a situation where it had not been done).
That the cabin pressure controller has been re connected after maintenance is another ( had that a couple of years ago).
That the center of gravity of the aircraft has been calculated correctly for departure. ( we just get a print out telling us what it is).
That the load is distributed in the correct holds in the belly of the jet as per the load calculations. ( we don't get told where it should be so can't tell if it is wrong).
That the dangerous goods we are carrying have been packed correctly and are separated when they should be separated.
That we don't have intoxicated passengers boarding the aircraft ( ground staff load them sometimes if they don't want to deal with the grumpy pax and the paperwork).
That the fuel loaded has been checked for water.
Etc etc etc
The are many things that we are technically responsible for that we have to trust other people to do.
That's just airline flying. But who is responsible for ensuring all those people are well rested and well trained and checked for competency? Take a guess......