A practical english grammar - Vyssaja skola 1978

The past perfect verb phrase
Sound symbols

The past perfect consists of had (the past of have) and the past participle of a verb. Its meaning is quite similar to that of the present perfect, except that the point of interest is some moment in the past, rather than “now.” It names events whose effects or results were still important at some past moment.

My father had been in London before, and so the experience of seeing the city was not new to him.

The past perfect is also a narrative tense. It relates past events that occurred before other events in the past.

I had seen him three weeks earlier.

The important use of the past perfect in expressing unreal conditions (If I had known . . .) will be discussed in Chapter 18.