Baron Karl Horst von Waldthausen came from an influential and important family who had established an industrial empire in Essen. Starting in the textile industry, they later invested heavily in coal and steel as well as in banking.
A very wealthy man, Karl was born in Essen though in 1914 with the on set of WWI the family moved to Liechtenstein and Switzerland where he lived in the Château Bartholoni in Versoix. A motoring enthusiast, he built a private circuit in the grounds of his villa. The local residents did not share his passion for cars and complained. Karl decided that the best thing to do was to move so he relocated to the Château Tatiana near Nyon about 20 Km further north on the shore of Lake Geneva, where he once again built a private circuit. He had Lichtenstein citizenship and was also know in Switzerland as Karl de Waldthausen. Later he became a Swiss citizen.
He provided financial backing for both the automobile and motorcycle Grand Prix on the Meyrin circuit in Switzerland in 1931. He started competing the following year when he joined up with Julio Villars to form the Equipe Villars-Waldthausen. Their first outing came in March at the 1km standing start Kilometer sprint at Grand Saconnex, just north of Geneva. Waldthausen drove a 1750 Alfa sports car while Villars drove a 1100cc BNC. The event was won by Hans Stuber in a Bugatti T51. At Develier-Les Rangiers in July he was third fastest of all cars, now driving an Alfa Romeo 8C-2300 Monza. Once again Hans Stuber was fastest. He was entered in the Grand Prix du Comminges at St. Gaudens in August with the 8C-2300 but did not arrive.
He was eighth in the 3-liter racing class at Klausen and a fine third at the Stelvio hillclimb Waldthausen behind Tadini and Caracciola. At Mont Ventoux he came third behind Caracciola and Benoist in the racing class up to 3000cc. He then drove a Steyr sportscar in the Rheineck-Walzenhausen-Lachen. At the end of the season Waldthausen and Villars came fifth and sixth respectively in the sportscar class of the Swiss Championship.
1933 began with the Grand Prix at Tunis where Waldthausen finished fourth behind Nuvolari, Borzacchini and Zehender. Then he retired in the next five races: Alessandria, Picardie, the Eifelrennen, the Grand Prix de l'ACF and the Marne Grand Prix. At La Baule in August he finally made it to the finishing fourth, behind the Bugattis of Williams, Marcel Lehoux and Benoit Falchetto, beating Count Stanislas Czaykowski's Bugatti to fifth place. At the Grand Prix de Comminges one week later, he finished fourth again, one lap behind Fagioli, Wimille and Guy Moll, all driving Alfa Romeo Monzas.
Then two weeks later at the Grand Prix de Marseille at the Miramas Autodrom he crashed in the south Turn on lap 20. It was reported that a tyre burst on his Alfa Romeo at high speed causing the car to roll several times. Karl was thrown out onto the concrete track, severely injured. He was taken by car to the medical post, from where he was transported to the Salon-de-Provence Hôpital where he was admitted at 5:30 PM. An hour later he succumbed to his injuries. He had sustained a double fracture of the right leg, a double fracture of his shoulder and other internal injuries. He remained fully conscious until the end.
After his fatal crash, Julio Villars sold up and quit racing.