Cussen, Denis John (1901–80), rugby international and athlete, was born 19 July 1901 at North Quay, Newcastle West, Co. Limerick, second son of Robert ‘Bob’ Cussen, solicitor, and Mary Cussen (née Moylan) of Newcastle West. Both his parents were members of prominent local sporting families, and his father had been captain of the first known Blackrock College rugby team (1882) and a founding member of the Irish Coursing Club at Clounanna (1904). Cussen attended St Catherine's convent and the Courtenay School in Newcastle West before completing his schooling at Blackrock College. He entered TCD in the autumn of 1919, where he studied medicine, qualifying as a doctor in 1925. While at Blackrock his overall sporting ability became apparent, both as a prolific try-scoring centre three-quarter and as an outstanding all-round athlete. He won three Leinster Senior Schools Cup winners medals in succession, captaining the winning sides in 1918 and 1919 and was a Leinster schools interprovincial player. His brothers, Jack, Bertie, and Mick, also won Cup medals with Blackrock, with Jack and Bertie playing on the same side as Denis. In athletics he won Leinster titles in sprints, the long jump, high jump, triple jump and shot put. Such was his reputation from schools rugby that he was selected for an international final trial while still playing for the Trinity second XV, a remarkable occurrence, and he made his international debut on the right wing against England at Twickenham (February 1921), a game that ended in a 15–0 defeat. He went on to play fifteen times for Ireland in the period 1921–7, scoring five tries, two of which were scored in his most famous appearance: a 19–15 defeat of England at Lansdowne Road in 1926. An 11–8 defeat by Wales denied Ireland a Triple Crown that year. At domestic level he was on three Leinster Senior Cup winning teams for Trinity (1920, 1921, 1926). He remained a Leinster interprovincial player until 1926, when he moved to London, and later played for St Mary's Hospital and the Barbarians.
His athletics career was also impressive, as he won the Irish 100 yards championships four times in the 1920s, the IAAA titles in 1921 and 1922, and the NACA titles in 1925 and 1928, when he set an Irish record of 9.8 seconds for the 100 yards that has never been bettered, and that was a world record at the time for a grass track. That year he represented Ireland at the Amsterdam Olympics, reaching the second round of the 100 metres competition. He also won national titles in the long jump (1921, 1922) and in the 220 yards (1921).
As a rugby player Cussen was a straight-running and tough winger who relied on his strength and speed to beat the opposition, but a measure of his ability is that he was a key player in an Irish side that included such luminaries as Mark Sugden (qv), Ernie Crawford (qv), George Stephenson (qv), Eugene Davy (qv), and ‘Jammie’ Clinch (qv), and which was unlucky not to win a Triple Crown. A medical doctor by profession, he initially worked at St Mary's Hospital in London, later went into general practice in London, and subsequently became medical adviser to the Shell Oil Company. In 1946 he was awarded an honorary doctorate by TCD. He continued his interest in sport and was a pioneer in the new speciality of physical medicine and a founder member of the British Association of Sport and Medicine. He was medical officer to the British Olympic teams in Melbourne (1956) and Rome (1960) and was one of the first people to congratulate Ronnie Delany after his Olympic victory in 1956. He died 15 December 1980 at his home in Richmond, Surrey, and was buried at Richmond.
He and his wife, Lillian, married in England, and had one child, Jill.