Sentences that begin with "Not until..."

Question

If a sentence begins with not until, what is the rule for inversion of subject and verb directly after not until?  Example: "Not until we had/had we reached the top did we realize how far we had come."  

Thank you,  

Serge, United States

Answer

The correct form of the sentence you are asking about is: 

• Not until we had reached the top did we realize how far we had come. 

When a sentence begins with the phrase not until, the subject and auxiliary verb in the first clause, immediately after not until, are not inverted ("we had reached"). However, in the second clause, the subject and auxiliary verb are inverted ("did we realize"). The grammatical structure of these sentences is shown in the diagram below. 

• Not until  [1st clause: subject + auxiliary verb...]  [2nd clause: auxiliary verb + subject...]. 

Here are some other examples, with brackets around the two clauses: 

• Not until [the rain stopped] [could we see the view of the ocean].
• Not until [the president resigned] [did the protests stop].
• Not until [my daughter called me] [did I stop worrying about her].

I hope this helps.