Gareth Gates has shared a sweet tribute to his rarely-seen daughter Missy.The Pop Idol star posted a photograph of him and his teenage daughter on Instagram as he branded her his "great achievement". Doting dad Gareth, 39, stood beside Missy, 15, in the snap, with the pair both glammed up in all-black outfits.The singer sported a blazer and matching top, while Missy looked stunning in a black off the shoulder top. "My greatest achievement in life is you @missygates_x," Gareth, who welcomed his daughter in April 2009 with ex-wife Samantha Gates, penned.