'x factor' bosses were so desperate to hire Britney Spears that they gave her permission to do whatever she wants.

The 'Toxic' hitmaker worried onlookers at a taping in Austin, Texas yesterday (24.05.12) when she disappeared during four auditions, later claiming she needed a break, but sources close to the production say producers were so adamant about getting her on board that she was able to negotiate terms that were previously ''unheard of'' including unscheduled breaks during filming.

A source told gossip website TMZ: ''Simon Cowell is a smart and shrewd businessman who knew Britney could make his show and he was willing to give her just about anything to come on board - and he did.''

Despite her walk-off Britney - who has joined Simon Cowell, L.A. Reid and fellow newcomer Demi Lovato on the panel in a reported $15 million deal - was a huge hit with the crowd during her first day as an 'X Factor' judge.

Insiders said a lot of her comments were met with huge cheers from the audience while it was revealed Britney - who had a well documented breakdown from 2007 to 2008 - was articulate, encouraging and funny at times.

Before the first audition both Britney and Demi took to twitter to share their 'X Factor' excitement.

Mother-of-two Britney wrote: ''So excited to be going to Austin this week for @TheXFactorUSA auditions! Will I see any of y'all there on Thurs or Fri? (sic)''

While Demi wrote: ''I'm so excited for the auditions today!!!! It's my first day... woo hoo!! Who's coming??!!! #XFACTORUSA. (sic)''