https://youtu.be/Yr5EztEPJS8?si=7xDQLpjgtI7RLjyX
This occured in 2013 when the crew of Ivatt Class 2 No.46521 left the derail open and rolled right off the tracks on the Quorn & Woodhouse line for the Great Central Railways.
Here's the aftermath:
https://youtu.be/a7ofOJsFRlk?si=7PCiReV0TWE-fqBi
https://youtu.be/qflXYQqbd4M?si=xokFDwK2_Ch0PoPZ
the line's website say nothing about this incident, and apparently it was only 2 years out of restoration when she went on the ground:
https://www.gcrailway.co.uk/the-railway/locomotives/46521-2/
I assume they got her running again as I imagine the damages wouldn't have been too bad.
But does anyone know what happened to the crew?
A friend of mine recently saw the video and really wanted to know, and after a while I got to wondering as well...

The wonderful world of Wikipedia says this about it.....

Can't remember what happened afterwards now as it was deemed to be an internal railway operating matter which was not subject to investigation by the UK Railway Accident Investigation Branch.
It got reported in the railway and local press at the time and lots of things were posted online, and then it got forgotten about after a while.....

.

As I recall, subsequent investigation revealed something akin to this:

*The signal was being pulled to clear the train for movement, but did not/would not move.
*The signalman in the box still hadn't pulled the derail points shut--they were controlled from the box and not a ground throw, not certain whether they were fully interlocked with the signals or not.
*Signalman verbally advised the crew of the defective signal and TOLD THE LOCO CREW TO PROCEED.
*The crew did so with the catch points still open.

I believe the blame gets split between the signalman overruling the signal verbally and the crew for failure to double-check the points.