What "Authorities", they'd have been reduced by 99% just like the rest of the world so, for example, out of 650 MP's there'd be 6 left, out of 160k police there'd be 1600 left (for the entire UK), out of 153k Armed Forces you're down to 1500 etc plus I'd guess nobody, anywhere in the world, would still turn up for work the next day after an apocalypse
Yeap, absolutely 100% agree on that! Afterwards it'd be whose able to adapt to living like its pre-industrial revolution again, due to low population, low technology use (it'd all be broken and unfixable within a short time) so back to full manual/animal labour, maybe some water wheels at most.