The past perfect continuous (also known as the ‘past perfect progressive’ or, more rarely, the ‘pluperfect progressive’ or ‘pluperfect continuous’) is a verb tense used to describe duration in the past. It is formed by combining three words: ‘had’ (the past tense of the auxiliary ‘to have’), ‘been’ (the past participle of ‘to be’), and the present participle of the main verb (i.e. ending in -ing). For example, consider the following:
We had been cooking for hours by the time the guests arrived.
In this sentence, the action (‘cooking’) began in the past and continued up until another point in the past (when the guests arrived).
In this way, the past perfect progressive indicates the duration of an action, not the action itself. (In the latter case, the simple past would be more appropriate.) See the accompanying figure.
There are three related but slightly different manners in which the past perfect continuous may be used to indicate duration in the past:
Duration Before Something in the Past
The past perfect continuous is most commonly used to indicate an action that began in the past and continued up until another past action or point in time in the past. This was the case with the sentence we considered above. Another example might be:
George had been smiling all the way home.
When used this way, the tense emphasises the duration of an action completed in the past.
Causation in the Past
The past perfect continuous is also frequently used to link an action or state with a separate ongoing action or state that caused it. When used this way, the action that’s more recent is indicated with the simple past, and the ongoing action that caused it is indicated with the past perfect continuous. For example:
Vegetables were expensive because supplies had been running low.
Interruption in the Past
When combined alongside the simple past in a sentence, the past perfect continuous can also be used to indicate the ongoing nature of an action until a point where it is interrupted by another action. For example:
I had already been sleeping when she barged into the room.
Recommended Read
Ilse Depraetere & Chad Langford, Advanced English Grammar: A Linguistic Approach. Bloomsbury Academic, 2019. See the book