GRAMMAR & STRUCTURE — Examples
Past Perfect Continuous

Past Perfect Continuous

Continuous Action (first past action)

Past Simple Action (second past action)

Explanation

I had been typing my report for an hour, when my boss told me he needed it.

had been typing

told me he needed it

The man typed from 10:00 to 11:30.
The boss told him he needed the report at 11:00.
Both actions are in the past. The typing continued even after the boss told him he needed the report.

Michelle had been running for half an hour when it got dark.

had been running

it got dark

Michelle ran from 5:15 to 6:00.
It got dark at 5:45.

Joseph had been waiting for an hour when the bus finally arrived.

had been waiting

The bus arrived

Joseph waited from 9:00 p.m. to 10:00 p.m.
The bus arrived at 10:00 p.m.

What had Gail been doing before she started working here?

had / been doing

started working here

Gail started working here in 1998.
The question asks what Gail was doing before she started working here.