Originally Posted by DDT
That phrase is correct but I can not tell you why. I know nothing about the use of "have or had" either.
BUT, many people will say that phrase as, "If you had have come in time, you wouldn't have missed the train."
Don't ask me about why there is a "had have" in their because I don't know. I don't even know if it is good or bad English but I can tell you that, that is how I would have said the sentence.
Also, I don't know why I just said "that, that"!
........I speak that way, too. :)
English is silly, isn't it? :wink: