GUIDE ENGLISH GRAMMAR BOOK

32 CONDITIONAL CLAUSES PAGE 338
b
We can use could + perfect in the if-clause.
If I could have warned you in time, I would have done.
We can use other modal verbs such as could or might+ perfect in the main clause.
If I'd written the address down, I could have saved myself some trouble.
The plan might not have worked if we hadn't had one great piece of luck.
NOTE
We can also use continuous forms.
If he hadn't been evicted by his landlord, he wouldn't have been sleeping in the streets.
c We can mix Types 2 and 3.
If Tom was a bit more ambitious, he would have found himself a better
job years ago.
If you hadn't woken me up in the middle of the night, I wouldn't feel so
tired now.
NOTE
We can also use a Type 1 condition with a Type 3 main clause.
If you know London so well, you shouldn't have got lost.
258 Should, were, had and inversion
The following types of clause are rather formal.
1 We can use should in an if-clause to talk about something which is possible but
not very likely.
I'm not expecting any calls, but if anyone should ring, could you take a message?
If you should fail ill, we will pay your hospital expenses.
NOTE
We can also use happen to.
If anyone happens to ring/should happen to ring, could you take a message?
2 Sometimes we use the subjunctive were instead of was. • 242(3)
If the picture was/were genuine, it would be worth thousands of pounds.
If it wasn't/weren't for Emma, I'd have no friends at all.
(= Without Emma,...)
We can also use were to for a theoretical possibility.
If the decision were to go against us, we would appeal.
3 We can express a condition with should or the subjunctive were by inverting the
subject and verb.
Should anyone ring, could you take a message?
Should we not succeed, the consequences would be disastrous.
Were the picture genuine, it would be worth thousands of pounds.
Were the decision to go against us, we would appeal.
We can do the same with the past perfect (Type 3, • 257(6)).
Had you taken a taxi, you would have got here on time.
Had the guests not complained, nothing would have been done.
But an if-clause is more common, especially in informal English.