Past Perfect Simple

Affirmative	She had won.
Negative	She had not won.
Interrogative	Had she won?
Form	had + past participle (past participle of regular verbs: verb + ed | Past participle of irregular verbs: forms differ and should be learned by heart.
Uses	action taking place before a certain time in the past sometimes interchangeable with past perfect progressive putting emphasis only on the fact (not the duration)

 Past Perfect Simple

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Past perfect tense

Form of the past perfect simple:

Had	Past Participle Form

Affirmative	Negative	Interrogative
I had worked.	I had not worked.	had I worked?
You had worked.	You had not worked.	had you worked?

NOTE:

I had not worked = I hadn't worked
I had worked = I'd worked

Use of the past perfect simple:

Use the past perfect tense to show an action that was completed prior to another action that took place in the past.
Examples:

•  "President Lincoln had attended the theater regularly before his assassination."
•  "They had had lunch when I arrived."