Past perfect

The Past perfect is used for an action that was completed at some point in the past before something else happened.

It is formed using  the past tense of the verb “have”  and the past participle of a verb

 

In the negative form, use the past tense of the verb “have” + not + the past participle of a verb

 

In the interrogative form, use the past tense of the verb “have” + subject + the past participle of a verb