Dear Casiopea,

So it means that:
(It was) not till he had arrived home that he found he had left it in the restaurant.


So he was on the way home.
And maybe he was driving, suddenly he found that he had left sth in the restaurant.
Is it right?


Why do we put auxiliary verb "did" there?
Not until he arrived home did he find he'd left it in the restaurant.
( the 2nd sentence is correct, isn't it? )

When would we put auxiliary verb in that position?
(I think this sentence is a little like
No sooner had I left the house than it started raining.)

When and Why?

Thanks!