Ronnie MacMahon competed in the individual and team three-day eventing at the 1972 Munich Olympic Games, finishing 24th individually on San Carlos – the best result of the Irish eventing team at those Games.

He was Ireland’s most successful eventing combination of the early 1970s: apart from winning the Irish dressage championship, MacMahon and San Carlos had finished second at Badminton in 1970, finished fourth at the World Championships, won the international championships at Punchestown in 1971 and won a team bronze at the European Championships that year.

MacMahon also represented Ireland in Nations Cup show jumping and in 1971, with Billy Ringrose and Ned Campion, won the Nations Cup at Fontainebleau.

He was the first officer of the AES to officially compete in three-day eventing. San Carlos was loaned to the AES by Sir John Galvin. In Munich, MacMahon was 26th after dressage (the best Irish performance), suffered a fall and two refusals on the cross-country, but jumped a clear round in the showjumping.

He went on to compete at the Montreal 1976 Olympics where San Carlos again represented Ireland, this time failing a drug test – though all parties were held blameless for a genuine therapeutic treatment that produced a positive result.