Counterfactual conditional clauses
The third type of conditional clause is the counterfactual conditional. In this type the event or state is presented as counter to reality: it didn’t happen. This is the highest degree of remoteness. The structure has If + a past perfect in the conditional clause, and a modal perfect (would + have + past participle of the lexical verb) in the main clause.
If you had given me a ring (BrE) /a buzz (informal) /called me (AmE), we might have met somewhere.
If anyone had asked me to carry a package on the flight I would have refused.
Subject-operator inversion with the auxiliary had is also a rather formal alternative to if in a counterfactual conditional clause:
Had you given me a ring/called me, we might have met somewhere.
The counterfactual construction is associated not only with conditional clauses; it can occur in other discourse contexts such as expressing regret or reproof at something that didn’t take place:
It would have been a pleasure to meet your son. (but we didn’t meet him)
You should have told us he was coming. (but you didn’t)
We would have very much liked to see the Cup Final. (but we didn’t)
