The X Factor has increased security after comedian Lee Nelson stormed the stage during Saturday night's live show.
The comic character - real name Simon Brodkin - was seen interrupting Stereo Kicks' performance, getting into the studio with a fake pass before being grabbed by guards.
Lengthy queues and checks were put in force for Sunday evening's results show, with procedures so strict that Manchester United and England defender Luke Shaw was denied entry to the show.
Next week all guests are going to have to provide photo identification.
A source revealed to The Sun about how Nelson got in: "He kept a pass from last time he was a guest and flashed it to get past security. Things like this can't be allowed to happen."
He has since revealed the motivation behind getting on-stage during the boy band's rendition of Michael Jackson's 'You Are Not Alone'.
"When I saw Stereo Kicks on telly there were so many of them I thought anyone could have a go. And when I heard one of them might not be able to make it as he had homework I decided to give it a bash ... 'X Factor' security waved me straight through. Stereo Kicks were great and all had smiles on their faces."