At the tender age of fourteen, Heerup left school to become an apprentice. To start with, he worked as a signwriter, lithographer, and bronze caster, but young Heerup did not like monotonous work and rigid conditions. Liberty came when he started working as a bike delivery boy, which offered him the possibility of being outside and making detours to places like the National Gallery of Denmark to study Rembrandt’s painting technique.

Already at this point, young Heerup wanted to become a real artist and on Midsummer Eve 1924, he painted his very first oil painting. Ulvedalsegen (The Ulvedal Oak), as he called it, was painted at the foot of an old oak in Dyrehaven and Heerup considered this coincidental with his own beginnings as an artist. Therefore, he celebrated the 10th, 15th, 20th, 25th, and 30th anniversaries of this event in style. As late as 1969, he painted Drengen i Ulvedalsegen (The Boy in the Ulvedal Oak), now recreating the experience with mature artistic eyes and expressive colours. The memory of his initial experience of painting never lost its power with Heerup.

That same year, he painted his first self-portrait in a naturalistic style showing him clad in a smock with a pencil and a drawing board in his hand. With his calm look of deep concentration, this early work indicates Heerup’s artistic ambitions and very special talent. He studied drawing from life under the painter Helge Helme as well as at Niels W. Rasmussen’s school of painting; in 1927, aged just 20, he enrolled at the School of Painting at the Royal Danish Academy of Fine Arts.

Heerup remembered the Academy as the best time of his youth. In the exhibition catalogue of the artists’ group Decembristerne from 1954, he wrote:

’This is me again (Class of 1907). We had a good time at the Academy – we really did. Thinking of my friends here at the Høst and Decembristerne [shows]. We are so very different, of course. But fired by the same flame.’

Heerup’s student years 1927–32 were highly formative and Academy professors became important associates. The symbolist Ejnar Nielsen took, with his eye for the expressive qualities of painting, great interest in Heerup’s expression and technical skill and Aksel Jørgensen, if any, opened the eyes of the young artist to both printmaking and motifs from everyday life. Besides these important sources of inspiration, Heerup always recalled the student camaraderie with great joy.