<Li> ^ Walsh served as a guest judge in place of Cowell during the fourth series, and Hasselhoff during the fifth series . </Li> <Li> ^ Electra served as a guest judge in place of Holden, during the sixth series . </Li> <Li> ^ Ant & Dec served as guest judges in the eighth series, substituting for Cowell on the first day of the Manchester auditions . </Li> <Li> ^ David Walliams' mother, Kathleen Williams, served as a guest judge in place of Cowell, while attending a session in the tenth series . </Li>

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