no sooner (do something) than (do something else)
One action had just concluded when something else happened or began. No sooner had I wrapped up the meeting than everyone bolted from their seats. She had no sooner taken the meal out of the oven than someone started knocking at the door.
Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.
no sooner...than...(written) used to show that one thing, which is unexpected, happens immediately after another thing: No sooner had she got in the bath than the front door bell rang.
See also: no
Farlex Partner Idioms Dictionary © Farlex 2017