If you consider the country ends of P8/9 and P10/11 they are both equally complicated 'works in progress' with only half of the eventual platform end built, on the P9 or P11 sides. So I think you might be getting unnecessarily concerned about this.
Fair comment - I'm sure it's all being done in an order that makes sense to the people doing it (or do I mean in charge of doing it?).
But, as you point out, the other end of P11 does look as if its face is finished to the end and halfway along the return, though missing its steel fence. P9 has a fence, and that will need altering when the nibbled corner of P8 is made good - presumably worth doing that way as the removal of the acrobatic link line from P8 can't be done until after the viaduct is up and running.
This all started with my puzzling over what the length of main line platforms would be, given that they started off much longer. That is not relevant for the trains and services being planned, but would be if there was ever a need to boost passenger capacity in a hurry. And that's part of the big imponderable topic known now as "resilience".
There is still something inside the Cabinet Office called the "Civil Contingencies Secretariat", which uses the strapline "How networks and individuals can support the country's emergency planning, response and recovery, and keep systems and services running." Transport is one of the main topics they address, though the little evidence I can see of their work is limited to natural hazards such as flood. It needs little imagination to pick that out, as it has happened. So has a disruption to oil supplies, so I would expect that to be on the list of hazards to plan for as well. The example we have was in distribution, so the effect was very quick, but threats further back in the supply chain could still reach crisis point in a few weeks.
Last time, in 2000, large numbers of people did switch to trains - or try to - but then it stopped after about a week. That's the point, really: railways have the capability to boost passenger capacity at short notice, but for a big boost you need longer trains and the platforms for them. Obviously you need to relax some of the rules on comfort and even safety. I am not sure whether the reserve of old rolling stock we used to have has physically gone, or is just not accessible via the leasing process, but resilience planning would also consider that. We seem to be drifting into a situation of only building platforms as long as the trains and then buying trains of fixed length that can't be made longer, or even coupled together to suitable length in a lot of cases. So what, if anything, is this bunch of resilience planners doing?
