Prenn was born on 7 September 1904 in Vilna, Russian Empire (current Vilnius, Lithuania)[11] to a railway building contractor, and was Jewish.

[2][5] Prenn represented Germany in the 1926 World Table Tennis Championships in London, reaching the fourth round in singles and the quarterfinals in doubles.

[12] In 1928 he won the singles title at the International German Tennis Championships, held at Am Rothenbaum in Hamburg, defeating Hans Moldenhauer in a three-set final.

[16] He also lost the doubles with his Davis Cup teammate Heinrich Kleinschroth to the duo of Tilden and Erik Worm.

[18] The same year he lost the Berlin International Championships the second time to Roderich Menzel in straight sets, but won the doubles partnering with him.

[21] He received the Reichsmedaille for winning the European Zone of the 1932 International Lawn Tennis Challenge, as the Davis Cup was then officially known.

[1] He then moved to England and represented Great Britain in the 1933 Maccabiade in Prague where he defeated Ladislav Hecht from Czechoslovakia in the final of the singles event.

[29] In 1935, he was the runner-up for the mixed doubles contest of the British Hard Court Championships pairing up with Evelyn Dearman.

[32] The same year he won the Surrey Hard Court Championships at Roehampton against South African player Pat Spence.

[33] In early 1931, he was accused of turning professional (meaning he broke the rule of amateurism) and was suspended from playing for a couple of months[19] before being acquitted, when it turned out that he had been mistaken for another person named Danel Prenn[34] Several months later the German Tennis Federation suspended him for another six months for sponsorship charges, based on the accusations of racquet manufacturer Hammer & Co. who claimed Prenn asked for payment for choosing Hammer's equipment.

He was also expelled from the Germany Davis Cup team, though it didn't affect his presence as Germany was eliminated in the first round of the 1931 International Lawn Tennis Challenge[35] On 24 April 1933, a newly appointed Reichssportführer issued a declaration on behalf of the German Lawn Tennis Association stating that no Jew could be selected for the national team or the Davis Cup, and that no Jewish or Marxist club or association could be affiliated with the German Tennis Federation, and specifically that the Jewish player named Dr. Prenn would not be selected to the German Davis Cup team in 1933.

[10] The Swedish king, Gustaf V, a keen tennis player, dined with the German top brass in the summer of 1933, criticizing the new racial policies.

[4][5][36] In an open letter to The Times leading British players Fred Perry and Bunny Austin protested again Prenn's exclusion from the Davis Cup.

1953), was a shareholder in Lacoste, and as an avid supporter of tennis and squash he got Celestion involved in a racquet sponsoring venture, which ended in 2010.