Cambridge Grammar of English Hardback with cd-rom a comprehensive Guide

The past perfect in conditional clauses 

355d

The past perfect must be used when there is past reference in a hypothetical

conditional clause with if:

I’d have been killed 

if I’d been caught down there.

(I would have been killed if I had been caught …)

Well, even 

if you’d come home tonight, you’d have been upset anyway.

(… if you had come home, you would have been upset …)

✪

The past perfect is not used in the main clause in a hypothetical conditional

sentence:

If I 

had had more time I would have been in touch earlier.

(If I had had more time I had been in touch earlier.)