Van der Hart was one of the players to play the "Watersnoodwedstrijd" of 12 March 1953, a match played in the Parc des Princes stadium in Paris to raise money for the victims of the North Sea flood of 1953. In 2003, Van der Hart told Dutch public broadcaster NOS that players such as himself and Bram Appel, Theo Timmermans, Bertus de Harder and Kees Rijvers had heard of the flood over the radio and realised their country was in a state of panic. While the KNVB, which still did not want to be connected to the professionals in any way, forbade the match, it went ahead after a personal intervention from Prince Bernhard. 8,000 Dutch fans travelled to Paris to attend the fixture and saw their team beat a strong French team 2–1. The match played a crucial role in introducing professional football in the Netherlands; In 90 minutes, the players showed the spectators how much further players could improve when they played the sport professionally. Only 17 months later, the first professional match in the Netherlands was played.