Cole at the 'end of her tether' over Cowell's practical jokes

Cheryl Cole is at the "end of her tether" with 'The X Factor'.

The 27-year-old mentor - who has two acts, Rebecca Ferguson and Cher Llloyd, in tonight's final - is reported to be at the end of a number of practical jokes from fellow judge Simon Cowell that are irritating her when she is facing the most important night of the show.