Study this example situation:

Yesterday morning I got up and looked out of the window.
The sun was shining, but the ground was very wet.

It had been raining.

It was not raining when I looked out of the window; the sun was shining. But it had been raining before.

Had been -ing is the past perfect continuous:

• When the boys came into the house, their clothes were dirty, their hair was untidy and one of them had a black eye. They'd been fighting.
• I was very tired when I got home. I'd been working hard all day.
• When I went to Madrid a few years ago, I stayed with a friend of mine. She hadn't been living there very long, but she knew the city very well.

• We'd been playing tennis for about half an hour when it started to rain heavily.
• Paul went to the doctor last Friday. He hadn't been feeling well for some time.

Compare have been -ing (present perfect continuous) and had been -ing (past perfect continuous):

Present perfect continuous	Past perfect continuous
- I hope the bus comes soon. I've been waiting for 20 minutes. (before now)	- At last the bus came. I'd been waiting for 20 minutes. (before the bus came)
- James is out of breath. He has been running.	- James was out of breath. He had been running.

• It wasn't raining when we went out. The sun was shining. But it had been raining, so the ground was wet.
• Katherine was sitting in an armchair resting. She was tired because she'd been working very hard.

• We were good friends. We had known each other for years. (not had been knowing)
• I was surprised when Lisa cut her hair. She'd had long hair since I first met her. (not she'd been having)

For a list of these verbs, see Unit 4A. For have, see Unit 17.