We form the Past Perfect by using had with the past participle:
Sub. + had + 3rd form of verb + object
Positive : l/you/he/she/it/we/you/they had finished
Short forms : 1/you/he/she/we/you/they'd finished.
Negative : l/you/he/she/it/we/you/they had not finished
Short forms : l/you/he/she/it/we/you/they hadn't finished
Questions : Had l/you/he/she/it/we/you/they finished?
Short answers : Yes, I had No, we hadn't
We use the Past Perfect to talk about an action in the past that happened at a time before another action in the past:
We use the Past Perfect to show that something started in the past and continued up until another action in the past.
· We had had that car for ten years before it broke down.
· By the time Avi finished his studies, he had been in London for over eight years.
· They felt bad about selling the house because they had owned it for more than forty years.
We normally use the Past Perfect if we tell the' story like this:
Vijay went home early. He had worked hard, (the story goes back)
But we normally use the Past Simple if we tell the story like this:
Vijay worked hard. Then he went home, (the story goes forward)