Coolmore Stud owner John Magnier has accused billionaire Maurice Regan of waging a campaign to try and “destroy” him. A letter sent by Magnier’s solicitors Arthur Cox to Regan, seen by The Irish Times, details text messages between the two men after last year’s High Court case over the Barne Estate. Magnier believed he had a deal in place to buy the 751-acre estate in Co Tipperary, but Judge Max Barrett concluded a sale had not taken place. It was ultimately bought by Regan. The letter said Coolmore’s prohibition on doing business with Regan’s Newtown Anner Stud was justified due to threats to destroy Magnier’s reputation and business.Magnier is being sued by Regan’s stud in the High Court for damages for alleged breaches of competition law after his horses were barred from Coolmore’s stud services. Regan’s complaint alleges that Magnier’s Ballydoyle racing group was given preferential treatment at the start of races in Ireland.Regan, who runs the JT Magen construction firm in New York and the Mercantile pub group in Dublin, has also complained that trainer Joseph O’Brien was told not to train Newtown Anner horses. In a letter sent on Thursday, Magnier’s solicitors said it was clear that Regan’s “animus” and “personal grievance” stemmed from a 1999 public auction where Regan and his father were the “disappointed underbidders” when Coolmore bought Anne’s Gift, a large farm beside Coolmore in Co Tipperary. The letter complained that Regan’s “sole focus” in the competition case was to “use them as a platform for making bald allegations in the media and elsewhere”, culminating recently in a 13,000-word interview in the Sunday Independent”. Magnier’s letter said Regan had publicised complaints he made to Horse Racing Ireland (HRI) and the Irish Horseracing Regulatory Board (IHRB) about Ballydoyle starting arrangements. However, it said HRI has since confirmed there was “no basis” for the complaint to it. The IHRB said, “the matter remains under consideration”.The letter from Arthur Cox said the complaints were “part of a wider campaign against Coolmore to make good on Mr Regan’s threats that he would destroy John Magnier”.It outlined how Regan was connected in business dealings with Luke Comer, a billionaire developer who is suspended from horse racing after his horses tested positive for banned substances. The letter said Comer had made “wild allegations” that Coolmore doped his horses.Comer has alleged that Coolmore paid his training manager Jim Gorman to contaminate hay in his yard before his horses tested positive for banned substances. Coolmore and Gorman have denied the allegation. The claims emerged publicly in a court application by Gorman to obtain a recording that allegedly contained a Coolmore executive talking about paying Gorman as part of a doping plot.The letter said the recording was “an undated, heavily edited and scripted two-minute audio file, which was evidently created to damage our clients”. It added that Coolmore’s decision to bar Regan’s horses had nothing to do with the Barne case. Instead, it said, the business relationship was damaged by “Regan’s desire to cause Mr Magnier personal harm”.It said this “encompasses your client’s threats that he would destroy Mr Magnier’s reputation and business ...”. The letter complained that Regan’s competition case was a “fig-leaf” used to “malign our clients and to prosecute what our clients consider to be Mr Regan’s one-sided feud under the veil of legal privilege”. Legal firm Creed McStay issued a response to Arthur Cox on behalf of Regan that dismissed its complaints as “a work of fiction”. It said the Comer allegations did not concern Regan and were “an irrelevance” to his competition case. Regan’s relationship with Comer was “a narrow one” concerning one investment, it added. The firm said Regan had intended to continue business with Coolmore after the Barne case but claimed Magnier “could not let the matter rest”. It denied Regan had nursed a grievance for 27 years, saying he had done business with Coolmore for 20 of those years. Comer was contacted for comment.