So, we have over two tonnes of Mk 3 Shoggie towing three-quarters of a tonne tare trailer and over two tonnes of mini-tractor (so about five tonne train weight). If the tractor moved during the "accident", it would tend to roll forward. However when I enlarged the photo, I noted there are straps over the rear wheels and they look up to the job. I doubt the tractor would have come off the trailer! Although we don't know the cause of death, I strongly suspect that coming to an abrupt halt from about 30mph didn't help. The front crumple zone on a Mk 2 is from the longditudinal chassis members, which are designed to fold from a frontal impact. That bollard impacted between those chassis members and managed to hang up on the front diff and steering rack, which would have forced the steering column rearward while stopping the car much more abruptly than hitting a brick wall at the same speed. IOW, these bollards are exactly the right shape and height to negate the frontal impact safety measures built into many cars.
BTW, something worries me about the legality of the signage used to warn of these bollards.
http://www.opsi.gov.uk/si/si2002/02311334.gif shows the requirements for a "no entry" sign, and no variations are permitted. I suspect that the plate "except bicycles and authenticated busses and taxis" is an unlawful variation, making the no-entry sign thus invalid, possibly making the bollards an unlawful obstruction of the public highway. However, I'm no expert - perhaps someone who knows how to unpick TSRGD 2002 would like to comment?