… because of course a unit that was working in Wales one week can’t possibly be suitable to work in the East Midlands the following week…Sheesh, the MDTR really doesn’t help itself, does it!
Not exactly an informed, or constructive contribution.

It is due an exam and powertrain change and couldn't, for whatever reason, be done by TFW according to my contact
Thanks for the informed, constructive contribution!
As is generally the case with railway operational matters, there is a perfectly sensible explanation, that isn’t immediately obvious.