Showbiz
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The 60-year-old, who is a close friend of the music mogul, insists that Cowell's X Factor commitments will obstruct any plans to marry the make-up artist in the summer.
He told the News of the World: "He won't be getting married this year - and he doesn't need to rush into it anyway. Simon has a lot to do.
"He has to prepare himself for The X Factor, to try to create the next biggest show [in the US], and he'll be fully focused."
Lythgoe added: "Maybe he's just gearing himself up. He hasn't really known Mezghan for that long. But she was my make-up artist for six years and she and Simon are a good fit. They can make fun of each other.
"[Cowell] knew [ex-partner] Terri Seymour for an awful lot longer. It must have been hard enough to propose for him."
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