1/ the rear power car, still under full power, caused much of the
crumpling and jack knifing, and

This is believed to be incorrect, but is in the interim HSE report
which might explain why it got posted here.

The unfounded idea that the rear power car was still under full power
was certainly NOT in the interim HSE report. It was an ignorant rumour
that I believe was mentioned first on Sky News a few hours after the
crash.
--

I can see where this has come about. There is a BBC website report that
states "The front of the First Great Western train ploughed into the
embankment, while the rear power car on the train continued to propel the
train forward, investigators found."

What they have missed out is "momentum of", which is in the HSE report.

...and the investigators might have pointed out that the momentum of the
rear eight coaches acting on the (derailed) leading power car was a lot
greater than the momentum of the rear power car.

David

I'm going to wander off topic here slightly... but i hope it's still
relevant.

Wasn't the Lockington accident made worse by the fact that a heavier
DMU set was at the rear?

If i recall correctly wasn't it a 105/114 pairing? Making it even
worse the 105 trailer car was leading (thus the lightest carriage of
the four), and class 105s being of shorter body length and pretty
appalling crashworthiness wise, would have made things worse. Shorter
bodylength being worse cos damage from front and behind on the first
carriage would be more catastrophic.

The 105 trailer struck the van on the level crossing and then the
heavier carriages behind kept it going and lots of track was damaged
leading to serious damage to all four vehicles.

So maybe there is a point about the heavier vehicles behind keeping
the train moving.

Slamdoor Mat.