Bushman's holiday

A 'busman's holiday' is a phrase which means that someone is doing the same thing on their day off as they would do at work. It usually means that they are doing it out of the goodness of their heart. In London in the 19th century, drivers of horse-drawn omnibuses were so solicitous of their horses' well-being that the drivers would often spend their days off surreptitiously riding as passengers on their own buses to make sure that the substitute driver was treating their horses well.