The pair head the market at 8-1 for the six-furlong dash after ending up in stall 13 and eight respectively following Thursday morning’s draw ceremony.
Markab was the ante-post favourite for the £100,000 prize, but was last of the full field of 28 runners to be drawn.
Stall 13 in the centre was the only option for trainer Henry Candy.
Blue Square’s Alan Alger commented: “Markab was favourite coming into the race, but after being left with stall 13 we have pushed him out from 7-1 to 8s, alongside Prohibit.
“The stalls on either side were first to be taken, but there is now plenty of pace in the middle and three of the last 10 winners have been drawn in stall 19.
“I can’t see a sustained gamble developing on the front two in the market, and support is likely to come for one of the bigger prices.”
With eight of the last nine winners breaking from double-figure boxes, last week’s Ascot fourth Genki could be one of those to attract punters’ cash after landing gate 10.
Roger Charlton’s lowly-weighted five-year-old is 14-1 with the sponsors – the same price offered about Saturday’s York winner Knot In Wood, who heads the handicap for the in-form Richard Fahey yard.
Dandy Nicholls is predictably mob-handed with six runners. Valery Borzov (15), Buachaill Dona (24), Sonny Red (26), Evens And Odds (16), Fol Hollow (21) and Striking Spirit (27) all line up.
Nicholls said: “Although we went for high numbers, I think there is also going to be pace on the stands side.
“I have walked the course and the rain will have made a bit of a difference, as will the new strip of ground that they have opened up.
“But it is a straight line at the end of the day and it is going to be a tough race to win.”
Last year’s winner Conquest broke from stall 14, and trainer John Gallagher chose the same berth for his 16-1 shot Mac Gille Eoin.
He said: “We just had to take what was left, but there seems to be pace around us and last year’s winner came from 14 so let’s hope lightning strikes twice.”
Advanced was the fifth-last horse to be called, with the 25-1 chance ending up in stall 17.
His trainer Kevin Ryan commented: “If I had had the choice I would have gone high but there is a lot of pace around him.”