Eddie Hayson has agreed to attend the next episode of the More Joyous inquiry on Monday along with ex-footballer Andrew Johns and former jockey Allan Robinson, who have also had a change of heart about appearing.

The controversial Hayson, a Sydney businessman and at times a big punter, had said he would not appear to answer questions over his part in events leading up to the public stoush between owner John Singleton and trainer Gai Waterhouse over rumours something was wrong with More Joyous before she finished second last in the All Aged Stakes on April 27.

Singleton has told the inquiry he received a call from Robinson on raceday passing on what Johns had told him regarding the mare's condition, information Johns said came from the trainer's bookmaker son Tom Waterhouse.

Both Robinson and Johns provided statements to the inquiry but were not available for cross-examination by Racing NSW stewards over inconsistencies in their accounts of the number of phone calls between the pair during the afternoon.

Stewards accessed records which show a greater number of calls between Robinson and Johns than were disclosed, with calls also made to Hayson.

Singleton sacked Waterhouse as his trainer via television interviews after the All Aged Stakes, saying she had a conflict of interest because her son was a bookmaker.

Last Monday's hearing became heated when Gai Waterhouse called Singleton a sham and said he was drunk on raceday, something he denied.

Tom Waterhouse's ledger showed a $300,000 worse result with the winner All Too Hard than if More Joyous, which he backed, had won.

Stewards established that More Joyous, who had heat in her neck, had received an antibiotic the day before the race on the instructions of Singleton's vet John Peatfield, who examined her on Saturday and passed her fit to run.

As her trainer, Gai Waterhouse was obliged to tell stewards if there were any issues leading up to the race.

Waterhouse said she did not regard it as an issue.