Query about inversion in eng

There are a number of ways to add emphasis to your sentences in English. Use these forms to emphasize your statements when you are expressing your opinions, disagreeing, making strong suggestions, expressing annoyance, etc.
Inversion

Invert the word order by placing a prepositional phrase or other expression (at no time, suddenly into, little, seldom, never, etc.) at the beginning of the sentence followed by inverted word order.

Examples:

At no time did I say you couldn't come.
Hardly had I arrived when he started complaining.
Little did I understand what was happening.
Seldom have I felt so alone.

Note that the auxiliary verb is placed before the subject which is followed by the main verb.

http://www.learnenglish.org.uk/grammar/archive/inversion01.html
Inversion involves putting an auxiliary verb before the subject of a clause. We do this in a number of different situations:
Questions
The most common use of inversion is in the forming of questions. We use the auxiliary verbs be (for progressive and passive forms), have (for perfect forms) and do (for most other forms). Modal verbs can also be inverted to form questions:


Were they ready when you arrived?

Where was it made?

Have you ever visited France?

Where do you live?

What should we do now?

http://www.ucl.ac.uk/internet-grammar/function/subjinv.htm
Negative and restrictive adverbs
In formal English, it is quite common to use inversion after negative adverbial expressions and restrictive words such as only, never, hardly and little.



At no time did he get permission for what he was doing.

Not until the next morning did she realise how serious it was.

Only later did they learn his terrible secret.

Never before have I seen such awful behaviour.

Hardly had we walked in the door when the phone started ringing.

Little do you know how much trouble you are in.