Racing:Robert Winston, Robbie Fitzpatrick, Fran Ferris and Luke Fletcher were all on hand as their hearing at the Horseracing Regulatory Authority began in London yesterday.
The four are accused of having provided information for reward or passing information that would subsequently be used for corrupt gain that otherwise was not in the public domain.
Winston and his weighing-room colleagues were present as the inquiry, for which officials have set aside 10 days, got underway at the HRA's Shaftesbury Avenue headquarters.
The hearing began at 9.30am before concluding for the day at around 4.30pm.
HRA spokesman Paul Struthers said: "We have begun presenting our case and the inquiry will continue tomorrow."
Five unlicensed individuals, including former bookmaker Ian Nicholl, also facing charges, did not attend yesterday.
Meanwhile, Anthony Ramsden, son of former trainer Lynda, and Robert Owen, two non-registered owners, have been charged by the HRA as the Mickmacmagoole affair continues to rumble on.
Ramsden and Owen were each found to own a one-third share in the horse despite James Roberts being registered with Horseracing Ireland as the sole owner.