Airwork blamed the MoD and BAe for issuing incorrect documentation.
Later confirmed in the Tornado Airworthiness Review Team (TART) report and other ARTs. The RAF Chief Engineer had issued instructions that documentation was not to be maintained, and pulled funding. Airworks would not have known this as the reports were only released recently. That policy meant that it was madness to let any such contract on anyone but the Aircraft Design Authority.
However, the terms "good engineering practice" and "tools of the trade" come to mind.