* The interrogative future in the past occurs only in sentences reproducing inner speech (conventional direct speech).
§ 54.The future in the past forms are mostly used in object clauses dependent on verbs in the past tense in the principal clause. None of them can be used in subordinate adverbial clauses of time and condition introduced by the conjunctions when, while, before, after, till, until, as soon as, as long as, if, unless, in case, on condition that, provided, etc. In all these clauses the corresponding forms of the past tense are used.
However the conjunctions when and if may be used to open object clauses, then the future in the past forms can be used if required by the sense:
She didn’t know when I should return.
I doubted if we should see him at all.
§ 55. The future in the past indefinite is used to denote simple facts, habitual actions and successions of actions in the future viewed from the past:
He said he would soon fake up French.
I knew she would still see him as often as she could.
He said they would start at dawn, reach the river in the afternoon and in an hour or two would proceed up
the road towards the cliffs.
The sun was setting. In an hour it would be quite dark.
§ 56. The future in the past continuous is used to denote an action in progress at a certain moment of time, or an action that is expected by the speaker as a result of a naturally developing situation, both referring to the future considered as such at a certain moment of time in the past:
And she thought, poor soul, that at this time next Sunday she would be approaching her beloved Paris.
Then she mentioned in a rather matter-of-fact way, that Jack would be calling the very next day.
§ 57. The future in the past perfect is used to denote an action completed before a certain moment of time in the future treated as such at some moment in the past:
He realized that he would have accomplished his task long before midnight.
In subordinate adverbial clauses of time and condition described above (§ 54) the past perfect is used to denote the same kind of action:
He said he would do it after he had seen me.
§ 58. The future in the past perfect continuous denotes an action in progress that begins before a certain moment of time in the future viewed from the past and goes on up to that moment and into it. It is an exceptionally rare form, which is hardly ever found in any text.
He said lie would have been living here for ten years next year.
§ 59.Though the future in the past form refer the actions they denote to the future (viewed from the past), their actual time reference is broader than that of the future, for the actions thus expressed may refer not only to the actual future but also to the actual present or the past:
He said he would call tomorrow, and I’m going to stay in till he comes. (actual future)
I said I should come today, and so I’m here! (actual present)
I’m so upset. He said he would come the day before yesterday, but he didn’t. (actual past)