Cheltenham officials have re-assured punters over fears cash from a �26.5m Belfast bank robbery could be laundered through bookies at the course. Managing director Edward Gillespie said police had told him there was no specific threat to the meeting.
"But we've advised bookies to be very vigilant and if there's any change to the normal pattern, to tell the police.
"The public should be re-assured - if they're offered a note they don't fancy they should ask for another," he said.
Police believe December's �26.5m raid on Belfast's Northern Bank was carried out by the IRA, though the organisation has denied any involvement in what was the biggest cash raid in UK history.
Gillespie said police had told him the meeting was not a particular target for those trying to launder the cash.
"But when there are lots of people and cash, there may be some people coming for that purpose," he added.
On Monday, Reuters news agency reported Felix McKenna, chief of Dublin's Criminal Assets Bureau, saying: "I would like to warn the bookies that there will be Northern Irishmen at Cheltenham bringing large amounts of cash and putting it down as bets.
"What better place to launder dirty money than the races? ... They will be there in their dozens," said McKenna who heads the Dublin-based inquiry into the laundering of the spoils.
Police are still searching for the bulk of the cash. They seized almost �3m during raids in Dublin and Cork last month.
The Festival, which has switched to four days this year, is a favourite with the Irish, with an estimated 5,000 racegoers making the trip over the Irish Sea every year.
About �4m in on-course bets is expected to change hands during the week.