What Had Been Happening Before Something Occurred
Past Perfect Continuous
The past perfect continuous expresses the duration of an activity up to another point in time in the past. The use of the past perfect continuous stresses that a certain activity had been going on before something important happened.
Example:
We hadn't been surfing long before she downloaded a browser plug-in.
They hadn't been working long before he opened the email attachment that disabled the entire network.
He had been working on creating ASCII pictures from old magazines for years before he found a market for the images.
Positive Form:
Subject + had + been + 'ing' form of verb + (object(s)) + time expression
She'd been promising plug and play peripherals for six months before he learned he'd have to configure the settings.
Negative Form:
Subject + had + not + been + 'ing' form of verb + (object(s)) + time expression
They hadn't been working long before he opened the email attachment that disabled the entire network.
Question Form:
(Question Word) + had + subject + been + 'ing' form of verb?
How long had you been listening to that podcast before you subscribed?
Past Perfect Contrasted with Past Perfect Continuous
The past perfect expresses something that finishes before another activity in the past. The past perfect continuous, on the other hand, expresses the duration of an activity at the moment something important happened in the past.
Past Perfect Examples:
I had already set up anti-phishing protocol before the conman called.
I had already organized the files alphanumerically before the boss announced the new organizing strategy.
Past Perfect Continuous Examples:
They hadn't been working long before he opened the email attachment that disabled the entire network.
How long had David Lightman been trying to play the game before he found the back door?