The 79 years old Den Hartog has received the highest honour from the KNHS for his services at national and international level. Den Hartog, still a very vigorous man, has filled many board and management functions closely associated with equestrian sports since his veterinary studie. Among other things, he was the veterinary adviser of the KWPN (Royal Warmblood Studbook of the Netherlands) and the KNHS for many years. Also he was part of various national and international veterinary committees. As team and competition veterinary, he was involved with the international pair and four-in-hand sport. At the FEI World Championship Four-in-Hand in Beesd Den Hartog is a member of the Appeal Committee, together with Gé König (NED) and Diana Brownlie (GBR).