The National Hunt jockey Robbie Dunne has been banned for 18 months, three of which have been suspended, after being found guilty of pursuing a campaign of bullying and harassment against his fellow rider, Bryony Frost, at the end of a six-day hearing of the case by the British Horseracing Authority’s independent disciplinary panel in London.

The three-person panel adjourned to consider its verdict on Wednesday and returned on Thursday to tell the rider that it had found him in breach on the most serious charge against him, that he had engaged in “conduct prejudicial to the integrity, proper conduct and good reputation of horse racing by bullying and harassing a fellow jockey”.

Brian Barker, the panel’s chair, told Dunne that its conclusion was that “a course of deliberate conduct over a significant period of time has been revealed”.

He added: “This progressed from distasteful targeting to deliberate harassment both on and off the course, including occasional cases of dangerous bullying [on the course].”

Barker commended Frost as a “truthful, careful and compelling” witness, and said that in taking her complaint to the BHA, “she has broken the [weighing room] code, knowing that isolation and rejection by some was inevitable”.

The panel, he continued, acknowledged that Mr Dunne believed after a race at Southwell on 3 September 2020 that Frost’s riding was had caused the death of his mount, Cillian’s Well. However, he said that panel had been “unable to accept his sweep of denials, criticisms [of Frost] and his reasoning”, pointing out that Gavin Sheehan, who gave evidence on Dunne’s behalf, had described him as a “piss-taker”, and that Dunne saw himself as “one of the elders of the weighing room and someone who expected his view to be heeded.”

Barker also suggested clearly that the panel’s finding raises questions that both the BHA and Professional Jockeys’ Association will need to address.

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In reviewing the “evidence and approach” of “jockeys of repute and valets, who probably find themselves in a difficult position”, Barker said the panel had “real concern” to what Louis Weston [for the BHA] referred to as “the weighing room culture … is deep-rooted and coercive, and in itself not conducive to the good health and development of modern-day race-riding”.

While Barker was delivering the panel’s decision, Frost was riding in a race at Warwick in which she emerged as a seven-length winner aboard Graystone.