The sub-category of past verb tenses, past perfect continuous applies when we want to indicate that a continuing action in the past began before another past action began or interrupted the first action. This tense is also called the past perfect progressive tense.

The past perfect continuous is used to show that something started in the past and continued up until another time in the past. This verb tense is related to present perfect continuous but differs in the sense that the duration does not continue until now. It stops before something else in the past.

Past Perfect Continuous

Subject + ‘had’ + been (past participle of ‘be’)+ verb-ing. 

She had been running in the rain.

• We had been arguing.
• He had been driving.

You can also shorten the statement:
Subject ‘d+been+verb+ing.

• She’d been running in the rain.
• We’d been arguing.
• He’d been driving

Past Perfect Continuous tense is an effective way to show cause and effect in the past.  “Mary’s legs ached because she had been dancing.”

The negative form of showing past cause and effect can also be employed using the past perfect continuous tense. ” John did not win the competition because he had not been studying.” Here’s an example of  the negative form of the past perfect continuous in the long and shortened version:

• I had not been shopping  (I hadn’t been shopping)

Another way that the past perfect continuous is to describe a completed action before something in the past. ” I had never seen such an amazing sight before I visited the Grand Canyon.”

To conclude our discussion on the definition and examples of usage of the past perfect continuous tense:  we use this verb tense when we want to express that a continuing action in the past began before another past action began or interrupted the first action.