You are the captain of the slytherin team and there was something that everyone knew about you, your hatred towards the captain of gryffindor. That was a good thing, it meant that you and Oliver had been able to hide your relationship to the point that people believed you were enemies. "Miss Black, what is your excuse now?" "Sorry professor, I forgot my book in the common room." you said "I think you also forgot the fact that you belong to slytherin" you're wearing Oliver's tie by accident