I work 35 hours a week, I never do unpaid overtime, and the culture where I work is that if someone can't do their job within 35 hours then they aren't working smart. Fair enough if you're 10 minutes late going for your lunch if you get caught up with something, nobody is bothered about that, but if you're consistently working to half five then something isn't right. I think that's the right attitude. I have worked in other places where the wrong attitude was arrive half an hour early, leave half an hour late and nobody wanted to leave while the bosses were still there - but of course nobody wants to be the person spotted as breaking the unwritten rule. I honestly don't think it was any more productive.