Grammar

What is this future in the past?

Well, as the name suggests, it is a way that is used to tell a plan or forecast of the future that you had in the past.
And it is done with was / were going to + infinitive.
So is the past of am/is/are going to, which speak of future plans we have now.

Was/Were going to...

Use to express and ask about intentions and plans that have changed.

Structure

subject + was/were + going to + verb a base form + complement

Would...

Use to express intentions or plans that change but only in a nominal clause after verbs such as: thought, believed or said.

Structure

subject + would + verb a base form + complement

For example:  

I was going to be on time, but then my car broke down. 

We saw that it was going to rain, so we went back home.

I thought they were going to be at the party. 

They were going to get married this fall, but they had to call off the wedding. 

Denials and questions with was / were going to

It can also be used was/were going to to form questions and denials. For example: 

I knew I wasn’t going to get the job, but I went to the interview anyway.

He decided he wasn’t going to move to London.

Q: Didn't you say you were going to ask her out?

A: I was going to, but then I found out she has a boyfriend.

Video to review

Perfect modals...

Use to express feelings and beliefs about past actions and events.

1. Regrets or Judgments: subject + should + have + past participle + complement.
2. Possibility: subject + may/might + have + past participle + complement.
3. Ability: subject + could+ have + past participle + complement.
4. Certainty: subject + would+ have + past participle + complement.
5. Conclusions: subject + must+ have + past participle + complement.