fromEnglish Grammar Today
No sooneris used to show that one thing happens immediately after another thing.It is often used with the past perfect, and usually followed bythan:
[event 1]They hadnosoonerarrivedthan[event 2]they were arguing.
[event 1]We hadno soonerstartedcookingthan[event 2]there was a power cutand we had no electricity.
Whenno sooneris used in front position, we invert the order of the auxiliary verb and subject. This is common in more formal and literary styles:
[event 1]No soonerhad they startedtheir walkthan[event 2]it started to rain.
See also:
Hardly
Adverbs