Perhaps I could offer a couple of observations here.
In my view ( based on a fair amount of research) the problems with the ATC glider fleet started in the 80s with a rushed procurement of a large fleet of GRP gliders and powered aircraft. The MoD (and the RAF) failed to set up the required systems for supporting this fleet, and appear to have operated for many years without an effective Design Authority.
This initial failure was then compounded by a long running and systemic failure to maintain the aircraft properly in service. Some on this thread like to blame 'civilianisation'. Sadly, the fault (in my view) lay with the failure of the responsible RAF engineers to do their jobs and MoD staffs who failed to properly manage and supervise the support contracts they had set up. I believe that the well publicised efforts to strip the MoD of engineering specialists (led by RAF VSOs) in the 1980s and 90s probably contributed to the MoD's problems. The upshot is that by 2013, the ATC fleet was non-airworthy, mainly due to gaping holes in the mandated airworthiness documentation chain. Various reports have confirmed serious gaps in the RAF's QA arrangements, and failures to implement airworthiness critical recommendations. There were also major failures in recording of repairs and retention of documentation. Basically, poor engineering practice.
The whole scandal was finally exposed not by an operational safety audit, but by 2FTS' failure to pass a CAMO audit by the MAA. Even worse, it then took 2FTS another 15 months to grasp the scale of the problem. In the end, it took a direct threat from the MAA to get them to sort out their engineering organisation. The recovery, as is well known, has been painfully slow and required the loss of 40% of the fleet.
It's a major scandal. School children were being flown in non-airworthy RAF aircraft. The costs to the taxpayer haven't been revealed but must be substantial. Sadly, to date, no-one has been held accountable.
Best Regards as ever to all those working hard to make ATC flying safe again.
Engines