Looking at his record, he has a surprisingly decent one. Don't usually see Frank Warren matching his fighter's tough. Is Alantez in with much of a chance of causing the upset? Williams is a European-level fighter who Warren and Co. try to pass off as World-level.
Boxrec ranks Fox the 94th best middleweight in the world and they rank Williams as the 11th best middleweight so it's a cherry pick without much chance of an upset.