Class 66(?) Derailment, removed/plain lined points...?

[Robinson102]

Pretty sure the OP is thinking of the East Somerset jct incident. That's the only one that involved partial plain lining of S&C.

From the reports I've found online, the above mentioned post of Aldwarke Junction fits far more with the picture I remember.

As it was a loco derailed, rather than wagons derailed, that I remember.