no sooner said than done
Accomplished immediately, as in He said we should leave and, no sooner said than done. This expression employs no sooner ... than in the sense of “at once,” a usage dating from the mid-1500s.
The American Heritage® Idioms Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.