The comedian is joining Simon along with Amanda Holden and Alesha Dixon for the brand new eighth series.
Simon and David's bromance was well documented on last year's show, with the pair constantly winding each other up on the panel.
"He's become very cocky," says David at yesterday's Britain's Got Talent auditions in London. "He's certainly cracking lots of jokes because he's very competitive."
The banter between Simon and David has continued this year, with David using a number of props to amuse the 54-year-old, including an inflatable doll with a feathered headdress!
"His jokes aren't really funny. They're more mean," David continues. "He's been making a lot of jokes at my expense."
The duo arrived in style at the auditions held at Hammersmith's Eventim Apollo, after David chauffeured Simon to the venue in a black Rolls Royce!
Continuing to speak about music mogul Simon, who is expecting his first child with girlfriend Lauren Silverman this month, David says: "He seems to be in a very good place. He's very happy and he's a lot of fun to be around.
"I'm excited for him and I think it'll be interesting to see how having a baby changes him."
As for who should replace Simon if he needs to make an emergency dash to be with Lauren, David says: "Julian Clary, Graham Norton, Alan Carr... Someone with a very similar personality to him!"
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