Long before intensive training programs became common practice for athletes, Jack Guest Sr. proved that hard work and dedication were the corner stones of a championship title. "Jack of Diamonds" fulfilled his dreams when he claimed the world diamond sculls title at the Henley Royal Regatta in 1930. Guest began his rowing career at Toronto's Don Rowing Club in 1924, and a year later moved to the Toronto Argonaut Rowing Club. He began rowing in crews of fours and eights but soon proved himself to be a brilliant single sculler. Guest claimed the Canadian junior and association singles titles in 1927. A keen rivalry soon developed between Guest and fellow Argonaut rower Joe Wright Jr. Guest and Wright were known as the rowing twins of Canada, not only because they were born on the same day, but also because they were constantly neck-in-neck for single sculling titles. Guest narrowly lost the coveted diamond sculls title to his rival in 1928. Despite any tension that might have existed between them, these two champion oarsmen combined forces later that year at the Olympics in Amsterdam, claiming a silver medal in the double sculls. Guest won the national single sculls title in 1929 but lost the diamond sculls to Wright once again. With a driving determination to reach the top, Guest returned to the Don Rowing Club and started a rigorous 12-month training program with coach Harry Arlett. During the winter, he built up his strength and stamina in the gym, and in the spring he perfected his form on the water. By the time he reached the 1930 Henley Royal Regatta in England, Guest was in top shape. He sped victoriously through all of his heats, while Wright was defeated by German oarsman Boetzelen. When Guest met Boetzelen in the finals, the race was almost anti-climactic. Guest effortlessly crossed the finish line 200 yards in front of the German boat to claim the diamond sculls title. After achieving his goal, Guest retired from competition, but he remained involved in the rowing world the rest of his life. He served as president of the Don Rowing Club from 1938-52, the Dominion Day Regatta Association from 1946-56, and the Canadian Association of Amateur Oarsmen from 1955-56. After managing the Olympic rowing team in 1956, he served as Director of the Canadian Olympic Association from 1960-68. In addition, Guest was the first Canadian elected to the International Rowing Federation (FISA) in 1969.