Grammar - Past Perfect Tense

The PAST PERFECT TENSE indicates that an action was completed (finished or "perfected") at some point in the past before something else happened. This tense is formed with the past tense form of "to have" (HAD) plus the past participle of the verb (which can be either regular or irregular in form):
    I had walked two miles by lunchtime.
    I had run three other marathons before entering the Boston Marathon .

Singular    Plural
I had walked    we had walked
you had walked    you had walked
he/she/it had walked    they had walked

Singular    Plural
I had slept    we had slept
you had slept    you had slept
he/she/it had slept    they had slept

Singular    Plural
I had been    we had been
you had been    you had been
he/she/it had been    they had been

Prior to the Revolutionary War, Washington had been a surveyor and land speculator.
Aunt Glad had invested heavily in the air-conditioning industry before the Great Crash of 1988.
She had swum the English Channel every summer until 1997.
How long had it been since you saw each other?