A dreich day in Scotland

How much sleep do you need?
 
At a party last night (yes, it’s that time of the year) the conversation got around to hours of sleep, and I was surprised to find a number of those present get up at 5 am and even 4 am regularly.
 
 One cycled all the way to Dunfermline on a  summer morning, a distance of 29 miles , arriving  before 6 am.
 
Some time ago I heard a talk by Alexander McCall Smith, best-selling author of No1 Ladies Detective agency series, and he was asked about his writing regime. He said he gets up at 4 am to write for a few hours then goes back to bed.
 
I need my 8 hours of sleep. How about you?