Clearly a bad day for the railways, and clearly we will now have to endure the deep irony of politicians of various parties on TV pontificating about the railways they have done nothing but screw up or "re-organise" over the last 25 years !
But somehow I feel we are all missing the point. Surely the real issue here is that there is no proper terminus station to run these trains into. When you look at the maps north of Gare du Nord, or various other European Termini, there are masses of lines running in and out of those stations.
I'm speaking not as an expert, clearly, but surely there is some argument for building the capacity to run these major termini in a sort of A/B format, so that if the A Lines are down for whatever reason, accident, engineering work, power failure, train failure, the B lines can still run and operate some level of service. By that I mean separate everything, Signalling, Power, the lot. Such systems are quite common in various industries where overall failure isn't an option. And clearly, you'd never attempt engineering work on both segments at the same time !
Or if not, building small links to at least allow a Southbound train or two to terminate in St Pancras, or Liverpool Street, (and the same links for the other main termini to deal with issues at any of the other lines.) A kind of Orbirail I guess, but with a North and South spur to each of the great main lines.
In other words, just shouting at a contractor and promising it's all fixed now doesn't do anything to improve the long term resilience of the overall system. That's what needs addressed.