once have we had の部分の文法について

Question

For ten years, our gift shop has been ordering toys from your company and not once have we had to issue any complaints about your products.

once have we had の部分は、どの様な文法の形となるのでしょうか？

poteco · Answer

... not once have we had to issue any complaints about your products.

not once 「ただの1度もない」という否定の意味を含む副詞句がSVの前にあるため、we have had  の部分が倒置になって、have we had となっています。

回答