He was the first designer to recieve the annual award from both the Danish design council and the Council for Arts and Crafts and was appointed Professor of furniture design to the Danish Royal Academy in 1987.
Gammelgaard belonged to a generation of skilful furniture designers who had their background to the very well organised Danish apprenticeship system. His apprenticeship was served at the workshops of C. B. Hansen in Copenhagen. Following this apprenticeship Gammelgaard studied under Grete Jalk and then became a visiting student at the Danish Royal Academy's furniture school working under Poul Kjærholm and Ole Wanscher.
Gammelgaard later worked in the offices of Arne Jacobsen, Mogens Koch, Steen Eiler Rasmussen and Jørgen Bo. During this period he undertook consultancy work for the UN in Somoa, where he designed his famous Tip-Top lampshade, followed later by work in Ceylon and the Sudan. In 1982 Gammelgaard began his association with Børg Schiang resulting in many of his most successful designs including the Crestrail and Skagen chairs.