The six-time champion jockey retired in 2016 following a career littered with big-race victories, although success in the St Leger did elude him - twice narrowly missing out with top-class fillies Ramruma and Quiff.
Fallon is now a regular face on British courses once more, with his son Cieren currently leading the race for the apprentice jockeys championship, and the 54-year-old is one of the star names taking part on Wednesday in what has become an annual event on Town Moor.
Noel Fehily rides Hammer Gun for trainer Derek Shaw. Fehily retired in March after a stellar career in which he rode more than 1,000 National Hunt winners - including in the King George VI Chase and Champion Hurdle.
Grand National-winning jockey Timmy Murphy is on board John Quinn's Ascot Week, Gold Cup hero Andrew Thornton is booked to ride Valley Of Fire from Les Eyre's yard and former jockey turned award-winning presenter Luke Harvey partners Richard Fahey's Windsor Cross.
Fahey saddles two runners, with Sammy Jo Bell on board Dubai Acclaim for her former boss.
Ollie Pears trains and rides Placebo Effect, while Brian Harding - winner of the race two years ago - is on Tim Easterby's One To Go.
The field of 16 runners is completed by Destroyer (Colin Bolger), Dream Walker (Jamie Mackay), Elusive Heights (Gary Bardwell), Kannapolis (Barry Keniry), Poet's Pride (Charlie Poste), Sands Chorus (Victoria Smith), Whatwouldyouknow (Derek McGaffin) and Flying Dragon (Adrian Nicholls).
Fallon's son Cieren is also in action later on the card, with two booked rides on Asoof and Roundhay Park.
The most valuable race on the opening afternoon of the William Hill St Leger Festival is the £40,000 DC Training And Development Services Scarbrough Stakes. This five-furlong contest has attracted seven sprinters, with the field headed by John Quinn's El Astronaute.
His chief dangers on ratings are the Charlie Hills-trained Equilateral and Clive Cox's Tis Marvellous, although John Quinn's Queens Gift finished three places in front of the latter when runner-up in the Beverley Bullet recently.
Scott Dixon's Dark Shot, the David Griffiths-trained Duke Of Firenze and Archer's Dream from James Fanshawe's yard are the other hopefuls.
