He's famed for his immaculate attention to image and vanity - but Simon Cowell looked grey and unshaven yesterday as revelations about his private life continue to make the headlines.

In the latest installment of Tom Bower's biography of the star - which is currently being serialised by The Sun - The X Factor boss admits he is bemused by rumours surrounding his sexuality.

Simon has insisted "I'm not gay".

In the book, he is quoted as saying: "If I was gay, why wouldn't I admit it? It wouldn't harm me and my mother wouldn't I admit it?"

"It wouldn't harm me and my mother wouldn't freak out."

According to the biography the rumours first started when Simon started trying to establish then-girlfriend Sinitta's career in the 1980s, which saw him trying to flog her song So Macho to the gay market.

In an effort to do this he also befriended gay record producer Ian Levine, who admitted he saw Simon as a "camp, silly, indecisive record producer".

It has been a tough week for the X Factor mogul, which has seen his secret affair with Dannii Minogue exposed, as he seems to be showing the strain as he stepped out in London last night.

An unshaven Simon was seen leaving Mr Chow's restaurant in London's Knightsbridge last night, after attending his opera group Il Divo's concert at the Royal Albert Hall.

However, he was spotted enjoying the company of a mystery brunette, after it was also revealed in the book that he has called off his engagement to make-up artist Mezghan Hussainy.

Yesterday Simon opened up about the 'unauthorised' book - which actually saw Simon grant the author hours of access to him.

Speaking to US website TMZ, he said: "What I would say about the book, and I have to say this, is that I've been very embarrassed actually this week.

"It's not my habit to kiss and tell. I've never done it. I've always tried to keep my private life private, and it is unfortunate. So I was feeling very embarrassed and not gentlemanly at all this week because it's just not my style."

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