All over bar the shouting
Of a contest, almost finished and where the result is virtually decided before the crowd’s final applause or derision, dates from the early 19th century c.1842. It was first used in sports contexts, probably in boxing matches or horseracing, before the eventual winner was announced and before the crowd vented its approval or disapproval. It is now used in other contexts besides sports e.g. in elections etc. In America, the more usual form is all over but the shouting.