In uk.d-i-y, Dave Liquorice wrote:

Might have been the same incident if you are refering to HP and MOD to
the north of Bristol... Though TBH the incident I'm thinking of must
be nearer 20 years ago now rather than 10.

I think we have a winner! That would be the one... it would be under
20 years ago, since I've only been in Brissle just under that long; and
the MoD site was initially a speculative property development put up in the
?late-80s/very-early-90s? property boom-n-bust, which then stood empty
with the fountain squirting forlornly for a ?couple of years? before HMG
decided that Abbeywood might be a great place to centralise MoD procurment.

Of course in a properly designed system once the mains goes and you've
switched over to your generators you should stay on your generators
until you've had it confirmed from the supply company that the
restored supply is secure and isn't going to go off again. Auto start
your generators but don't auto switch back to the mains.

I do believe this lesson was taken firmly on board after the above
excitement ;-)

Stefek