When do we use Past Perfect?
The "past of the past"
Past Perfect describes an action that happened BEFORE another past action. Think of it as the "past of the past" — it goes one step further back in time.
When two things happened in the past, use Past Perfect for the EARLIER one.
When Oliver arrived, his grandpa had already left.
"had left" = earlier; "arrived" = later
She was tired because she had worked all day.
"had worked" = earlier; "was tired" = later result
I ate the cake that my mum had made.
"had made" = earlier; "ate" = later
Describing whether something had happened before a specific past moment.
Oliver had never seen the diary before.
"never" + Past Perfect
It was the best film he had ever seen.
"ever" + Past Perfect
She had never been to Paris before that trip.
"never...before" + Past Perfect
Past Perfect = the EARLIER action. Past Simple = the LATER action. "When she arrived (later), he had already left (earlier)."