Apparently if the civil servants make an effort to come to work but find the doors locked then it is ok for them to have a day off too.
I remember being a Civil Servant stood outside my locked office at 0800 waiting for 'someone from the Guardroom' to turn up with the keys. This happened every Tuesday following a Bank Holiday when the RAF didn't expect to slope in until lunchtime(ish) and that included those who I'd been drinking with all weekend in the Mess.