Happen to do es una estructura verbal que significa "dar la casualidad de que" o "por casualidad".
I happened to be at the airport when the king arrived.
He happened to give some very useful information.
They happen to have a very nice Rolls Royce you could hire.
I happen to know that she's going to leave him.
She happens to disagree with you.
Esta estructura también es una forma muy educada y bastante común de preguntar o pedir algo.
You wouldn't happen to know what time it is, would you?
You wouldn't happen to have a light, would you?
You wouldn't happen to speak Italian, would you?
Excuse me; you wouldn't happen to know where the station is, would you?
