Petrus Kastenman took up riding in 1941, when he enlisted with the Swedish cavalry regiment K1 in Stockholm and later served with the K3 cavalry regiment in Skövde. The high point of Kastenman’s career was at the 1956 Olympics, when he won the Olympic gold in individual eventing, held in his homeground of Stockholm because equestrian events could not be held in Australia due to quarantine regulations. Kastenman also won team eventing bronze at the 1957 European Championships. After retiring from the force in 1969, Kastenman built an eventing course in Borgunda near Skövde, which has hosted many major tournaments over the years. In the 1970s and 1980s he was also head coach of the Swedish national junior and youth eventing teams, the Norwegian and Finnish national eventing teams.