Past perfect simple tense

Structure of past perfect simple
positive negative question
I / you / he / she / it / we / they
had gone.
I / you / he / she / it / we / they
hadn’t gone.
Had
I / you / he / she / it / we / they
gone?
Past perfect simple – common mistakes
Common mistakes Correct version Why?
I didn't been to London. I hadn't been to London. We use the helping verb had (negative = hadn't) in the past perfect.
When I saw him, I noticed that he had a haircut. When I saw him I noticed that he had had a haircut. The action (a haircut) happened before the other past action (I noticed). We use the past perfect for the action which happened first to make the time order clear to the listener.
He told me has been to London. He told me he had been to London. His original words were: ''I have been to London.'' However, in reported speech we move the tense back – the present perfect (have been) becomes past perfect (had been).