Trainers Gai Waterhouse and Adrian Bott are at the centre of a stewards investigation for substituting horses in public gallops on the course proper at Randwick in Sydney.

Racing NSW stewards began the investigation after being alerted three horses from their stable on a running sheet for Tuesday's Breakfast with the Stars were, in fact, not the ones that galloped.

The course proper gallops were restricted to horses nominated to race in The Championships races at Randwick on Saturday and were filmed by Sky Racing.

English, who ran second in last Saturday's TJ Smith Stakes, was one of those listed to gallop when, in fact, the less well-performed Sort After wore her colours in the work-out.

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Serena Bay and Debonairly were also on the running sheet but their colours were worn by the riders on Stampede and Fabrizio respectively.

Dual group one winner Global Glamour did work as scheduled.

A Racing NSW stewards release said the investigation had so far established English, Serena Bay and Debonairly did not work as programmed and were substituted by other horses, carrying the same colours as the nominated horses.

Stewards said they had instructed Waterhouse and Bott to attend an inquiry at a date and time yet to be determined.