Tips - past simple and past perfect

I saw him yesterday.

I didn't (did not) see him yesterday.

Did you see him?

 I'd (I had) seen him.   

You hadn't (had not) seen him.

Had you seen him?

I worked in London.

In positive sentences, a helping verb such as 'was' or 'did' is not used.

Did he work in London?

The helping verb 'did' is used in past simple questions.

Did he work in London?

The helping verb 'did' is used in past simple questions.

Did he write a letter?

The main verb is used in the infinitive form in questions and negatives.

He didn't write a letter.

The main verb is used in the infinitive form in questions and negatives.

I hadn't been to London.

The helping verb had / hadn't is used in the past perfect.

When I saw him I noticed that he had had a haircut.

The action (haircut) which happened before another past action must be put into the past perfect to make the time order clear to the listener.

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 - present perfect (have been) becomes past perfect (had been).