We distinguish two uses of the Past Perfect Continuous: the Past Perfect Continuous Inclusiveand the Past Perfect Continuous Exclusive.
1. The Past Perfect Continuous Inclusive denotes an action which began before a definite moment in the past, continued up to that moment and was still going on at that moment. Either the starting point of the action is indicated or the whole period of duration. The preposition for is used to denote the whole period of duration. Since is used to indicate the starting point of the action.
We could not go out because it had been rainingsince early morning.
We could not go out because it had been raining for two hours.
He had been entertainingat restaurants for thirty years and he knew how to
assure the smooth passage of the meal. (Bennett)
As has been stated above (see § 21), the Past Perfect Inclusive isused to express an action which began before a definite moment in the past, continued up to that moment and was still going on at that moment, with verbs not admitting of the Continuous form, in negative sentences and with certain non-terminative verbs.
With verbs not admitting of the Continuous form the Past Perfect Inclusive is the only tense possible.
In negative sentences the Past Perfect Continuous Inclusive can be used, but it is far less common than the Past Perfect Inclusive.
With certain non-terminative verbs both the Past Perfect Inclusive and the Past Perfect Continuous Inclusive are used.
He said he had workedfor twenty years. (The fact is emphasized.)
He said he had been workingfor a long time without achieving final results. (The process is emphasized.)
The Past Perfect Continuous Inclusive is rendered in Russian by the past imperfective.
I had been readingabout an hour when he came.
Я читалоколо часа, когда он пришел.
2. The Past Perfect Continuous Exclusive denotes an action which was no longer going on at a definite moment in the past, but which had been in progress not long before.
I sobbed a little still, but that was because I had been crying, not because I