The proposed crew escape system fitted to the VC10K was complete nonsense.
The first few VC10K courses were taught how it was to be used and we listened with incredulous disdain.
The idea was that the aircraft could be abandoned having given away all its fuel to tanks dry - or nearly so as we still needed some eletrical and hydraulic power. The Air Engineer would operate a low level override button on the fuel panel, then spill the pressurisation to reduce differential pressure so that operation of the crew escape chute wouldn't cause an explosive decompression. Then the chute would be extended after which the crew was supposed to take turns diving out.
However, it was impossible to fly in parachutes as the seats wouldn't accomodate them. Also when the chute was operated, the sealing strip around the external door would most likely be ingested by the left hand engines, which would probably explode.
To add to the joy, we were supposed to use a walk round portable oxygen cylinder each as the cabin pressure rose. Thus we were supposed to unstrap, transfer to walk round oxygen, walk back to the cabin and don parachutes. One pilot would stay at the controls until the other had kitted up, then he would go back whilst the other pilot held the aircraft straight and level by leaning over the seat and holding the control column! After the chute had been deployed and everyone else had gone, the remaining pilot was supposed to leg it back to the cabin and dive out....if he could. No intercom of course, so any communication would be by shouting after releasing one's oxygen mask. The rubber jungle would also have dropped automatically as cabin altitude increased.....
In the K3, the wretched thing was right over the access hatch to the underfloor area. So if the Air Engineer needed to go downstairs, he had to do a limbo dance to wriggle down through the hatch. The BWoS test crew tried to convince us that it was easy when the first K3 arrived and we went on board to study it.
We were issued with immersion suits and bone domes (I think?) and there was a storage area in the squadron built for the purpose. I think that we did the single seat dinghy drill at SCSR as well as the multi-seat, but I might be wrong.
Eventually 'They' had an attack of commonsense and the whole nonsense was removed, leaving just a differential pressure gauge and part of the structure - which was the perfect size to hold a gash bag for galley rubbish etc. Which became known as the 'Million Pound Dustbin'.
There was no plausible scenario for use of the system and it certainly couldn't be used to abandon a damaged aircraft. Those who'd been rear crew in Victors thought their system was bad enough, but the proposed VC10K2/3 system was laughably ridiculous!