From 1948 to 1951 he was involved with CoBrA. He went on to join the Situationist International.
In 1959 he produced Stavrim, Sonetter a book of poetry illustrated by Jorn.
In 1960 he founded the Situationist Bauhaus based at the farm Drakabygget with Jorn.
He is the editor of Drakabygget, a journal about art and social philosophy.
On March 15, 1962 Nash was excluded from the SI along with Ansgar Elde. Both had been on the central committee and were accused of conspiring with certain art collectors. In the tract Danger! Do Not Lean Out , Elde with Nash and Jacqueline de Jong, had defended Ervin Eisch, Lothar Fischer, Dieter Kunzelmann, Renee Nele, Heimrad Prem, Gretel Stadler, Helmut Sturm and Hand-Peter Zimmer who had been excluded on February 10, 1962. These were the Spur group who had joined the SI. Nash had co-edited their magazine Spur. Danger! Do Not Lean Out said that although there may be grounds to criticise Spur, the way they had been expeled was totalitarian. The SI, at the behest of Jeppesen Victor Martin described those they had expelled as nashists''.
Following his exclusion he became involved in the Second Situationist International and the creation in 1974 of the Situationist Antinational.
In 1963 became an honorary artist of the Royal Danish Academy of Art.
He has exhibited at: