Diederik learned the equestrian sport at an early age. His father Alex van Silfhout is a well-known national and international dressage rider and runs his own dressage stable in Lunteren.

In 2003 Diederick achieved for the first time the participation at the National Championships for Juniors and won the third place with Luxform’s Olympus.  He got a reserve spot on the Juniors team, which was going to the European Championship in Saumur. In 2004 he and Luxform’s Popeye won the fourth place as an individual and the second place with his team. In 2005 Diederik won the third place on the National Championship, the first place with his team and the fifth place with his individual test with Luxform’s Olympus. Diederik made his debut in the Grand Prix with the fox stallion Dalwhinnie’s Forum, which used to belong to his father. A year after this Diederik won the third place during the National Championship in the Third level with his KWPN approved stallion Paddox. Diederik did a great job and won both the individual and the teamprice at the European Championship for Juniors.

Beside that Diederick achieved a lot of great international results with different horses. At the National Championship in 2007 won the bronze medal with Ruby. That same year he won the European Championship with his team. At the National Championship in 2008 he won the silver medal, also with Ruby. At the European Championship in the Portuguese Azeitão he won two times the golden medal, one time the silver medal with and he won the World goblet for Young Riders in Frankfurt, this all with his horse Ruby. With Vorst D, Davidoff and Ruby he did a good job during the international competitions in 2009. Ruby ended on the fourth spot, good enough to take part of the team at the European Championship in Ermelo that year.

After his Junior/Young Riders period Diederik became part of the A-squad of the Future Test. He rode a lot of beautiful competitions that year like Jumping Amsterdam, Aachen, Rotterdam and Den Bosch and won here a lot of beautiful prices.

In 2011 he scored the fourth place during the Winter Championships in Ermelo with Ruby. During the National Championship in De Steeg Diederik also achieved the fourth place with Luxform’s Popeye with rates of almost 70%. In the Freestyle itself he scored 73% and the fourth spot.

During the European Championship in 2011 Diederik won the Future test with Ruby. With Popeye he became once third and once fifth with rates of 70%  in the U25.

In August 2014 Diederik, rididing KWPN approved stallion Arlando NH N.O.P (- Paddox) made his international debut in August 2014 at the Alltech FEI World Equetrian Games in Normandy and got the bronze medal in the Team Competition. In the individual GP test he finished on 9^th place and in the Freestyle to Music he improved his personal best record: 77.29%. Diederik was called by team coach Wim Ernes to compete in these World Games just one week before the start. 

In February 2015 Diederik performed very well at Jumping Amsterdam with a 4^th place in the GP Fereestyle and scored almost 80%. In the FEI individual dressage ranking Diederick and Arlando NH N.O.P. is now on 21^st place. 

March 14, 2015. After his great performances in the Grand Prix at the international event  “Indoor Brabant “Diederik is now ranked on 17^th place with Arlando NH N.O.P in  the FEI individual dressage ranking, being now the fourth Dutch rider after Edward Gal, Adelinde Cornelissen and Danielle Heijkoop.  

July 2016: DIEDERIK AND ARLANDO:
                                                 CHAMPION OF THE NETHERLANDS 


June 4, 2015 Arlando is now on place 15 FEI Dressage individual ranking.