The music producer will take the place of Michael Ball on Friday when the actor takes time out to coach the soap stars in singing for theatre.
Gest declared he would play a full role in the show and insiders said they expected him to live up to the reputation he earned on I'm A Celebrity.
“I’m not going to the show to pick my nose," he told TV Biz. "I’m going to pick a star.”
And a show source told The Sun: “We all saw how outspoken David was in the jungle so there could be fireworks when he’s a guest on the judging panel on Friday.
“He doesn’t mince his words and also has a unique turn of phrase. David has vast experience of the music business so he’ll offer some good insight.”