The six-year-old headed into quarantine in Newmarket on Thursday before an outing in the Group One handicap on November 6, for which he is as short as 10-1.
Since joining Williams, the son of Makfi is two from two – having claimed the Chester Cup on his stable debut before tasting Group Three success in the Henry II Stakes at Sandown on his most recent start in May.
Williams said: “Magic Circle went into quarantine on Thursday in Newmarket. Everything has been fine. We’ve kept things simple, and everything has been straightforward.
“He doesn’t know he is running in the Melbourne Cup – as far as he is concerned, it’s just another race.
“I’m not nervous yet – but I will probably will get nervous the week before the race.
“We’ve been busy enough with other things. If it was the only thing I was focusing on for the last three months, it would have driven me insane.”