Dont they usualy just turn trains at West Hampstead during disruption at St.Pancras with passengers finding there own way via FCC/LUL?
They normally turn trains at kentish town, but this was not possible due to the isolation, the nearest neutral section to st pancras is graham park (half way between mill hill and hendon), so when the power went off nothing south of graham park was moving, west hampstead box were just stoping trains in platforms (including me with a nice 50 minute wait).
The stricken hst was stopped at the signal just under the nll, this is probley why the juice went off and affected eurostars on the international side, as there is no physical elecrtical connection in the overheads between the mml and eurostar, but there is between the nll and eurostar.
The said stricken hst was finally moved back to the first unelectrified lines which are the hendon lines behind cricklwood station, this is where i passed it heading south, it had been moved back to cricklewood by the time i came north again.