I suspect it will depend on how severe the situation becomes, and whether National Grid ESO decides to prioritise the rail network, but a few options are:
- Bimodes requested to all switch to diesel to limit the network's electricity draw (lightest option)
- Pre-announced rolling blackout, leading to cancelled electric services but no stranded trains. Diesel services may still operate
- rolling blackout without prior notice, leading to stranded trains (the railway industry will clearly do a lot to avoid this from happening)