A. Form

The past continuous is formed with was/were + the -ing form of the verb: I/he/she/it was/was not (wasn't) working.

You/we/they were/were not (weren't) working.

Was I/he/she/it working? (Yes, I/he/she/it was working./No, I/he/she/it wasn't working.)

Were you/we/they working? (Yes, you/we/they were working./No, you/we/they weren't working.)

B. Points of time in the past

We use the past continuous to talk about an action or activity that was in progress at a particular moment of time in the past:

At 3.15 yesterday afternoon, Mr Jansen was seeing some clients in London.

We can use the past continuous to talk about an action or activity that was already in progress, and which was interrupted by another action:

We were discussing our expansion plans when the chairman suddenly

announced his resignation.

We can rephrase this sentence using while + the past continuous:

While we were discussing our expansion plans, the chairman suddenly

announced his resignation.

The activity may or may not continue after the interruption:

Paul was doing some filing when his boss asked him to fetch an invoice.

(Paul fetched the invoice and then probably carried on with the filing.)

Paul was doing some filing when the fire broke out.

(Paul probably stopped doing the filing at this point.)

With a time clause like when the phone rang, we can use either the past continuous or the simple past.

The past continuous tells us what was happening up to the point when the phone rang:

When the phone rang, I was talking to a client.

The past simple tells us what happened afterwards:

When the phone rang, I answered it.