Past Perfect Tense

Form:
had + Past Participle (the "third form" of the verb)
I had already left the office when you phoned.
He had never seen snow before moving to Denmark.
We had finished our dinner by the time he got home.
You had tried so many times that everyone was surprised when you finally succeeded.
They had never met before that party.

Use:
A past action, completed before another past action or a past moment. Used when we want to emphasize that the action took place BEFORE something else in the past.
For example in the sentence:
I left the office around 5 and you called after that, around 6.
we would not use past perfect, here we have simply consecutive past actions, and we prefer the past simple. Saying
I had already left the office when you phoned.
I would emphasize that I was not in the office anymore. By the time the phone rang, my leaving the office had taken place.

Exercises