Inversion means putting the verb before the subject.
The normal order of words is reversed or inverted, generally to add emphasis or forcefulness, or to give special effect. It also sounds quite formal.
The part we want to emphasise is generally at the beginning of the sentence.

Although inversion of the verb before the subject is a common phenomenon in English sentences, it is seldom used in everyday speech, except in questions and with 'so/neither'.
It is more often found in formal statements or in writing.
In a sentence with no special effect or emphasis, the normal order of words is retained.

Example 1 : I have never seen such a beautiful rose.
Example 2 : Never have I seen such a beautiful rose.

In example n°2 above, inversion is used to emphasise the fact that in your whole lifetime you have not seen such a beautiful rose.

When can we use inversion?

It is sometimes difficult to remember when inversion is or can be used. Here are some guidelines and examples to help you.

In normal everyday English, inversion is used :

• To make questions : Does he?   Can you?
• After 'so', 'neither', 'nor' :  So do I, neither do I, nor do I. ( more here...)
  

In written English, as well as in a very formal style, inversion can be used in the following cases :

• After negative adverbial expressions  :
  • Under no circumstances can we accept credit cards.
  • Under no circumstances can we allow dogs in the restaurant.
  • In no way can he be held responsible.
  • At no time did she say she would come.
  • At no point was the price mentioned.
  • By no means is it easy to overcome shyness.
  • In no way do I agree with your methods.
  • Never before have I witnessed such violence.
  • Never before had I been asked to lie.
  • Never again will I return to that hotel. It was awful!
  • Not for a moment did I think I would get the job!
  • Not once did he offer to help me.
  • Not once during the first interview was the salary mentioned.
  • Not since my childhood have I had so much fun!
  • Not since the beginning of records have they noted such high temperatures.
  • Not until I heard my name did I believe I had won the race.
  • Not until the doorbell rang did I think my father would come.
  • Nowhere had it happened before.
  • On no account should you climb onto the roof.
  • On no account should you allow children to use these scissors.
    
    
• After adverbial expressions of place :
  • Round the corner came the postman.
  • In the sink sat a stack of dirty dishes.
  • On the doorstep was a bunch of flowers.
  • At the main entrance stood a policeman.
    
    
• After 'seldom', 'rarely', 'never', and 'little':
  • Seldom have I seen such a beautiful view.
  • Rarely did he pay anyone a compliment.
  • Never had I felt so happy.
  • Little did he imagine how dangerous it would be.
    
    
• After 'hardly', 'scarcely', 'barely', 'no sooner', when one thing happens after another.
  • Hardly had I begun to speak when I was interrupted.
  • Scarcely had we started our meal when the phone rang.
  • Barely had they finished the match when the rain started to fall.
  • No sooner had I arrived than they all started to argue.
  • No sooner had he closed his eyes than he fell asleep
  
  ► Note: hardly, scarcely and barely are followed by when; no sooner is followed by than.
  
  
• After adverbial expressions beginning with 'only' and 'not only'.
  • Only after the meeting did I realize the importance of the subject.
  • Only by working extra hours could they afford to buy a car.
  • Only if the weather improves will the picnic be confirmed.
  • Only then will they publish the final result.
  • Only when the plane landed safely did he calm down.
  • Not only was the food plentiful, it was also delicious.
  • Not only could she sing, she could also play the piano.
  • Not only was the car slow, it was also very uncomfortable.
    
    
• In sentences with 'little did' (somebody know, realize, think, imagine, consider ...)
  • Little did the soldiers know that worse was to come.
  • Little did the girl realize the value of the necklace.
  • Little did Emma think that she would not see her boyfriend again.
  • Little did the musicians imagine the welcome they would get.
  • Little did the influencer consider the impact the images might have on young people.
  • Little did the author know that his book would be so successful.




• Conditional structures with inversion :
  In conditional sentences we can sometimes replace the 'if' with an inversion:
  • If we were to tell the truth, it would not be believed.
    With inversion: →Were we to tell the truth, it would not be believed.
  • If the negotiations were to become known, there could be protests.
    With inversion:→ Were the negotiations to become known, there could be protests.
    
  • If I had known it would be so difficult, I would never have enrolled.
    With inversion: → Had I known it would be so difficult, I would never have enrolled.
  • If he had driven more carefully, the accident wouldn't have happened.
    With inversion: →Had he driven more carefully, the accident wouldn't have happened.
  • If the meat had been cheaper, I would have bought more.
    With inversion: → Had the meat been cheaper, I would have bought more.
    
    
• After exclamations with 'here' and 'there' :
  • Here comes the winner!
  • Here comes the bus!
  • There goes the bell!
  • There goes all our money!
    
    
• After 'as' and'than' in comparisons:(formal)
  In formal language, generally written, we can use inversion after ‘as’ and ‘than’ in comparisons.
  Inversion after a comparison is optional rather than required.
  • 'AS:
    - The children are bilingual, as are their parents.
    - I knew the answer, as did Tony.
    - The dessert was delicious, as was the main course.
    - We were short of money, as were most people in our situation.
    - She believed, as did her colleagues, that the plan would work.
    
    
  • THAN:
    Inversion is less commonly used after ‘than’.
    - The girl speaks better English than do her parents.
    - The French eat more often in restaurants than do the British.
    - Parents often watch more television than do their children.
    
    Inversion cannot be used when the subject is a pronoun.
    - We now know a lot more about outer space than we did fifty years ago.
    (NOT…than did we…)
    
    
• After 'so/such' …'that':(formal)
  • 'So + adjective + verb ... 'that'
    - So expensive was the journey that they had to borrow money.
    - So strange were my surroundings that I couldn't sleep.
    - So shocked were they by his rudeness that they walked out.
    - So exhausted was the hiker that he went straight to bed.
    
    
  • 'Such' + verb + noun ... 'that'
    - Such is the success of the product that we are going to increase production.
    - Such was the wind that we couldn't open the door.
    - Such was their excitement that the children couldn't stay quiet.
    - Such was her fear that she couldn't utter a word.
    
    
• With verbs of reporting such as 'say' or 'ask' in direct speech:
  • "I love you" said Harry.
  • "How far is it?" asked the passenger.