Apart from horns Dennis had one big passion: he loved cars. At orchestral rehearsals he often had a car magazine on the music stand instead of his music (he knew the music from memory anyway). His first car was an open Morris 8 with two seats. He shared it during the war with his brother to motor from Uxbridge into London. Later he had several cars. Whenever a car did not work he bought another instead of repairing it. He loved to drive and would often drive all the way home after a concert even if it was 100s of miles. Elisabeth Schwarzkopf let him drive her huge Hudson saloon car over the Gotthard Pass in Switzerland when it was officially closed because of heavy snow. On another occasion Herbert von Karajan let him drive his Mercedes 300SL. Once he bought a very rare 1939 12-cylinder Lagonda, but he soon crashed it and it could not be repaired. Other cars included a Citroen and a green TR2 sports car.