According to The Sun, the singer believes that there is a spirit in the Mulholland Drive mansion he shares with wife Ayda Field.
"The dogs can see it," a source told the paper. "Its nickname is Bertie. They believe it's a man from the beginning of the 20th Century."
They added: "Rob likes to imagine him in a suit holding a Martini glass."
Williams once claimed that he had been visited by a UFO.
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