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.
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. no sooner ... than
As soon as: No sooner was the frost off the ground than the work began.