learn it! title
Inversion after negative expressions and 'only...'
at night

Jana from The Czech Republic asks:

I have tried to learn English via the BBC, which is great! I like your Quiznet, but I need an explanation for the fifth item of Quiz Three: 5.
Choose the correct answer:

Only at night ..... the safety of their cave
bats leave

bats will leave
leave bats
do bats leave

Why is it not possible to use 'bats leave'? I would like to acquire this grammatical rule.

Roger replies:
Quite often in English, certain expressions with a restrictive or negative meaning are placed at the beginning of a sentence. The reason for doing so is to emphasize the point that you want to make. It is striking, original or surprising in some way. And whenever you make such a statement, inversion is necessary. So, it has to be:
  • 'Only at night do bats leave their cave.'
  • 'Only after I had returned home did I realize that I had left my watch in Emma's bathroom.'

Inversion is also used after the not only ... but also construction:

  • 'Not only did we visit Cuba's capital, Havana, (but) we also spent three days exploring the Galapagos Islands off the coast of Ecuador.'
Inversion is also found in expressions containing the word 'no', when placed at the beginning of the sentence:
  • 'Under no circumstances are you (allowed) to walk home from school alone.'
  • 'In no way will I agree to sharing an office with Ben.
The same rule operates for 'seldom', 'hardly', 'scarcely', 'rarely', 'never', 'never before' and 'no sooner':
  • 'Never before had I seen such realistic dinosaurs as there were in the BBC television series.' (This is a reference to a recent BBC series. If you want to know more have a look at the web site - Walking with Dinosaurs.)
  • 'No sooner had I arrived at the station than the train came in.'
  • 'Rarely do we see such brightly-coloured birds.'
  • 'Seldom do we walk on such green grass.'
  • 'Scarcely had we finished lunch when the bell rang for afternoon classes.'
Remember, you are registering surprise, or something similar, when you do this. If it is inappropriate to be so emphatic, you would say:
  • 'We had scarcely finished lunch when the bell rang for afternoon classes.'