Richard Johnson and Barry Geraghty are among the riders who will take part in the Mondialiste Leger Legends Classified Stakes at Doncaster.
Johnson retired from the saddle in April of last year following a glittering career – during which he won two Cheltenham Gold Cups, a Champion Hurdle and a Queen Mother Champion Chase.
He also rode more winners over jumps than any other jockey bar Sir Anthony McCoy – who won the Legends race in 2015 – and was crowned champion National Hunt jockey on four occasions.
Johnson will partner Michael Bell’s Greek Kodiac on Wednesday, in a race which was first run in 2010 and has so far raised more than £1million for Jack Berry House and the Northern Racing College.
Geraghty, who won the 2003 Grand National aboard Monty’s Pass and rode 43 winners at the Cheltenham Festival, will be on board the Charlie Hills-trained Mumtaaz on Town Moor.
Johnson and Geraghty are two of 13 former riders who will contest the charity event.
Sammy Jo Bell, who won the race two years ago aboard Dubai Acclaim, is this year riding Fennaan – trained by her partner Phillip Makin.
Brian Harding (First Dance/Tom Tate) and Noel Fehily (Vasco da Gama/Gay Kelleway) are also in the mix.
The most valuable race on the opening day of the St Leger Festival is the £80,000 Japan Racing Association Sceptre Fillies’ Stakes, which has attracted a field of 12 runners.
Likely contenders for the Group Three contest include Ivan Furtado’s stable star Just Beautiful, who was denied only narrowly in a Group Three in France on her latest appearance.
John Quinn saddles consistent filly Highland Princess – runner-up to Space Blues in last month’s City of York Stakes – while Jessica Harrington’s Loch Lein and the Henry de Bromhead-trained Wren’s Breath both travel from Ireland.
Potapova (Sir Michael Stoute) and Sweet Enough (John and Thady Gosden) also feature.
Last year’s winner Tarboosh faces six rivals in defence of his crown in the Listed Cazoo Scarbrough Stakes.
Paul Midgley’s veteran sprinter is taken on by a handful of familiar names, with Robert Cowell’s Arecibo setting the standard on ratings.