Zero hour contract
If you have a zero hour contract, and you agreed with your employer to work on a certain day, then you are entitled to at least three hours of salary.
For example: you and your employer agreed on Monday that you will work for a day on Wednesday. When you arrive at the company on Wednesday, it turns out that there is less work for you (in comparison to what you were recruited for). After about an hour all the work is done and you are sent on your way. In this case you are entitled to at least three hours of salary, despite the fact that you only worked for about an hour.