The TV star and her model fiance were all smiles yesterday as they partied with friends at the coveted music festival, and kept slipping off away from the crowds to spend time on their own.
A source told BANG Showbiz: "They just look so happy together. Luke was very attentive and affectionate, and kept stroking Kelly's hair, rubbing her back and looking lovingly at her. Even when his friends turned up to party, he kept checking Kelly was ok."
The pair - who got engaged in March last year - kept popping into the PlayStation 3 SingStar area throughout the afternoon to escape the sunshine and relax away from the 150,000-strong crowd.
Despite being in the public eye all her life, Kelly - who is the daughter of rocker Ozzy Osbourne and his wife Sharon - seemed rather self-conscious.
The source added: "When a photographer asked Kelly and Luke to pose for a picture in the SingStar party, she panicked about her appearance and asked him if she looked alright. She said she was worried she looked spotty and tired, but she actually looked lovely."