Wille Grut was a true multi-talented athlete. He was the son of Torben Grut, a top Swedish tennis player and a noted architect who designed the 1912 Olympic Stadium in Stockholm. Willie Grut was a talented swimmer, winning several freestyle titles in the 1930s, as well as a water polo title. He was picked for the Swedish relay team in Berlin, but did not actually compete there. However, in Berlin Grut learned about the modern pentathlon, a sport he took up afterwards. Being an officer with the Swedish artillery, Grut had the opportunity to train regularly in each of the five disciplines, and soon became one of Sweden’s best pentathletes - Sweden being the leading nation in the sport at the time. He would likely have been a top contender for the 1940 Olympic gold, had the Games not been cancelled due to war, so Grut had to be content with five Swedish titles: 1938-1940, 1944 and 1948. After the war, Grut first competed in the Winter Olympics, where a demonstration winter pentathlon was held. This was essentially a modern pentathlon competition, but with the cross-country running event replaced by cross-country skiing and swimming replaced by a downhill skiing event. Grut finished second in that competition, finishing behind compatriot Gustaf Lindh. Unlike Lindh, Grut also qualified for the actual modern pentathlon at the Summer Games, and Grut dominated that competition. He won three of the five events, and scored a record of only 16 place-points, for one of the most dominant modern pentathlon victories in international competition. The Svenska Dagbladet awarded him with the newspaper’s coveted gold medal for the best sports performance of the year.
Grut, who had also won several Swedish rifling titles with his artillery regiment, subsequently retired from sports, but he remained active and coached Lars Hall to a gold medal at the 1952 and 1956 Games. In 1960, he appeared as Sweden’s flagbearer at the Olympic opening ceremony. That same year, he was elected as the secretary general of the International Modern Pentathlon and Biathlon Union (UIPMB), a post which he held through 1984.