I seem to have read somewhere that the Nimrod problem was caused by the joints in its internal fuel lines, which were designed for normal operation, being too weak to take the high pressure involved in in-flight refuelling which was not part of the original Nimrod concept and design.
Usual MoD waffle in response. Never any acceptance of responsibility. And what about the Chinook crash due to known software problems which the air marshals blamed on dead aircrew who couldn't answer back?