Judge's pearl of wisdom: "This is a British competition and you make me very proud to be British. You've really got to me" - Simon Cowell.
Superstar advice: "I think Alexandra can belt her voice too much. I noticed she was getting a bit raspy. She really needs to have lots of lessons and make sure she doesn't lose that voice" - Will Young.
Alexandra has sung songs by divas like Christina Aguilera and Donna Summer
Has she ever been in the bottom two: No.
Trivia: Alexandra nearly made it through to the competitive stages of X Factor in 2005, but Louis Walsh turned her down, saying she was too young.
Tabloid "scandal": Ex-boyfriend D'Andre West is trying to sell a "graphic 10-minute video" which will "shatter beautiful Alex's dreams of superstardom". [News Of The World]
Favourite X Factor moment: Meeting Take That - "When I was younger I was such a big fan! I had Take That pillow cases, Take That bed sheets, Take That wallpaper - everything!"
On the final: "Whatever way the voting goes on Saturday night, I'm going to leave with my head held high knowing: 'Oh my God, I've actually made it to the finals' and that's an achievement in itself."
Bookmakers' odds: 8/13
Singer Marvin Humes was in boyband VS, who toured with Blue
Members: Marvin Humes, 23; Jonathan "JB" Gill, 21; Ortise Williams, 21; Aston Merrygold, 20.
Location: London and Peterborough.
Mentor: Louis Walsh.
Audition song: If You Ever - Shai, made famous by East 17 and Gabrielle.
Recognisable feature: Each member has a "signature colour". Marvin is green; JB is yellow; Ortise is red; Aston is blue.
Which successful act are they most like: 3T, the briefly-successful 1990s boyband formed by Michael Jackson's nephews.
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