west lakes thanks for your informative post. I currently have 10 x 3MVA 11kV DG sets on the high seas in open top containers - but without exhaust, cooling or daily service tanks fitted. Hence not 'portable' in your sense of the word and that's why I said 'just about fit...'. Agreed the logistics of bringing in that sort of power capability in an emergency are horrendous. And expensive. (Aggreko do very well out of the back-up business.)
My point was more that something of the order of 5MW of permanently installed stand-by diesels would probably have kept much of the N Term in some sort of functionality. (Shut down Maccy Ds and the Shops etc.....).
For all I know, LGW N. Term already has that level of backup power source -but it was also affected by whatever took out the mains power?