People in the top 10% of earners, how many hours a week do you actually work for that?

So to currently be in the top 10% of earners in the UK, you need to earn over £68k. I don't know anyone offhand who does who isn't self-employed, thus don't have a good point of reference other than my Uncle who was a lawyer in London (6 figures in the 90's). My early memories of him are working on Christmas day alone upstairs while everyone else was having fun.

How common is the culture of working all hours in these high paying jobs, rather than a normal 40 hour work week?