'Unusual and unprecedented': Minister says backup generator also hit by fire

Energy Secretary Ed Miliband tells Sky News there was a backup generator but that it was "also affected by the fire".

He says it shows "how unusual and unprecedented" the situation is.

And, he adds, it is "too early to know" what caused the substation blaze.

Describing it as a "catastrophic fire", Miliband says he has spoken to the National Grid about the situation.

He adds that his heart "goes out" to those impacted but that he is "reticent to jump to conclusions" about what has happened.