Britain's Got More Talent presenter Stephen Mulhern revealed that Cowell is worried new judge David Walliams will cause mayhem during semi-finals week.
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Mulhern said: "I'm worried what David will be like at the live shows, there's no controlling him!
"Simon did say he was contemplating having a 90-second delay because of David."
Hosts Ant and Dec recently claimed that the Little Britain star made jestful sexual advances towards Cowell while filming the auditions.
Britain's Got Talent returns for its sixth series this Saturday (24 March) at 8pm on ITV1, with Mulhern following with Britain's Got More Talent on ITV2.
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Watch the trailer for the new series of Britain's Got Talent below:
View a gallery of Britain's Got Talent 'first look' audition pictures below: