CORONATION Street and Emmerdale bosses are going to extreme lengths to keep the upcoming crossover totally secret.

The ITV soaps will come together for a one-off special early next year that will see characters from both soaps appear together for the first time ever.

And with filming set to begin in the coming weeks, The Sun can exclusively reveal that nothing has been seen as too extreme to keep the plot of the highly-anticipated episodes a secret.

A source said: “The soaps have assembled a top team working secretly on the crossover away from the usual productions.

“Every precaution has been taken for the event that’s set to begin filming later this month.

“Only the actors involved have been told what’s to come and sworn to secrecy.

“It’s practically unheard of to go to these lengths but bosses desperately want viewers to be surprised.

“The others have been left totally in the dark. It’s part of a huge fightback by ITV for the soaps’ relaunch next year when they go to the new transmission pattern.

“It’s being seen as a big reset to have a power hour each weeknight.”

One thing that viewers will find out before the episodes air is some of the cast involved as ITV will invite fans to vote on which two characters from each soap will share a scene together.

Meanwhile Emmerdale star Danny Miller has promised the episode will feature “high drama”.

Speaking on a podcast, he said: “The one thing [bosses have] said is that it won’t be someone walking into the Rovers and going ‘Oh I’ve got the wrong pub’, it’s not going to be like that.

“They don’t want to make it look like it’s just a p**s take.

“They want to make it a really good, high-end drama.

“I hope they do. Soap for me has changed my life.”