At the time, the Ryder Cup Deed of Trust required players to be born in and resident in their respective countries.

Joe McCartney, Hugh McNeill and Willie Nolan were tied after three rounds with Mahon one of those four strokes behind.

[6] Mahon had his best finish to date in a major British event in the 1934 Dunlop-Southport Tournament at Southport and Ainsdale Golf Club.

[12] The next week he was back in England for the final stages of the Daily Mail, where he finished tied for 27th, winning £10.

[14] Mahon was runner-up in the Irish Professional Championship for the fourth time in five years, four behind Joe McCartney.

He returned to play in the Irish Professional Championship at Portmarnock in mid-August, winning the event by 10 strokes.

[23][24] The team for the 1937 Ryder Cup was selected on 8 June following the conclusion of the Yorkshire Evening News Tournament, a match-play event in which Mahon lost at the last-32 stage.

[25][26] The Ryder Cup Deed of Trust had been revised in 1929 to require players to be born in and resident in their respective countries.

[28][29] Because of the delayed finish, the Southend Tournament marked the final event for the Harry Vardon Trophy competition.

Played at Royal Portrush, Mahon scored 291 to finish 6 strokes ahead of Willie Nolan.

[31] Because of his position in the 1937 Harry Vardon Trophy standings, he was invited to play in the Penfold Professional Golf League.

[34] Mahon continued to play in the Irish Professional Championship, leading after the first day in his final appearance in 1944.

[35] Shortly before his death, after more than ten years at Royal Dublin, he became the professional at nearby St Anne's Golf Club.

[36] Mahon was the professional at Royal Dublin when, on 2 August 1943, the clubhouse and adjoining residence, where he and his family lived, were totally destroyed by fire.