Firstly, remove 'if' because inversion makes it unnecessary. Then invert the subject and the first verb. So instead of 'I' first and 'had' second, it is 'had' first and 'I' second. Had I known, I would have taken a different route. Only the sub clause can be inverted; the main clause is not inverted. It stays the same.

To rewrite the sentence using inversion for formal/emphatic style, follow this structure: Had + subject + past participle, subject + would have + past participle Original: If I had known about the delay, I would have taken a different route. With inversion: Had I known about the delay, I would have taken a different route. This form is formal and often used in writing or speeches for emphasis.

thank you

So nothing is changed ?

Had I known...., I would have taken...