The Alvechurch handler's pair feature among 52 entries that remain in contention to contest the prestigious two-and-a-quarter-mile handicap.
Although London Prize has not been seen since winning the Northumberland Vase at Newcastle in July, Williams does not expect the six-year-old's fitness to be an issue.
He said: "London Prize will run in the Cesarewitch and Byron Flyer is destined to join him. London Prize has had a holiday and has been freshened up by the break.
"He probably had a bit more to do than I anticipated after his break, that is why he didn't go to the Doncaster Cup. I've done plenty of work with him and his preparation has gone well."
While Byron Flyer was narrowly denied a first Flat turf victory last time out in an extended mile and three-quarter handicap at Doncaster, when finishing second for the fourth race in succession, Williams believes the step up in trip will be in his favour
He added: "Byron Flyer ran well at Doncaster and gets in off a handy enough mark. I am sure he will appreciate a step up in trip. He has been very consistent.
"There is no question about his attitude and he deserves to win a race. It would be nice if it is this one."
Ante-post favourite John Constable and Cape Caster represent Evan Williams, while Hughie Morrison, who won the race 12 months ago with Sweet Selection, is responsible for Fun Mac, Star Rider and Aurora Gray.
Willie Mullins is another chasing a first victory in the race and has left in Laws Of Spin, Digeanta, Lagostovegas and King Of The Picts.
Other notable contenders include the Charlie Fellowes-trained Endless Acres and Who Dares Wins, who is one of four possibles for Alan King alongside First Mohican, Oceane and Couer De Lion.