A native of Brussels, Edouard Léon Théodore Mesens was an author, artist, publisher, curator, and dealer associated with the Dada and Surrealist movements, which he tirelessly promoted throughout his lifetime. His private collection, which probably originated in the early 1930s, included works by René Magritte (in 1932 he purchased around 150 works by the artist), Georges Braque, Paul Klee, Pablo Picasso, and Kurt Schwitters.
Initially trained as a musician, early on Mesens turned to poetry, photography, and collage as the preferred mediums for his artistic expression. As a teenager he joined avant-garde circles in Brussels, through which he met and befriended the artist René Magritte, whose work he would exhibit and sell throughout his career.
During the 1920s, Mesens worked for the Brussels art dealer Louis Manteau, at Geert Van Bruaene’s Galerie La Vierge Poupine, and at Paul-Gustave Van Hecke’s Galerie L’Epoque. In 1930 he opened the short-lived Galerie Mesens, and served as secretary of the Palais de Beaux Arts, Brussels (1931–36). Throughout this period, Mesens established relationships with many Surrealist artists and supporters, including André Breton, Paul Éluard, René Gaffé, Man Ray, Schwitters, and Tristan Tzara. Mesens met many of these artists during regular visits to Paris, and he organized exhibitions of their work in Brussels, including Le Nu dans L’Art Vivant (February 1934) and Exposition Minotaure (May–June 1934), both of which took place at the Palais des Beaux-Arts, and the International Surrealist Exhibition at the New Burlington Galleries in London (June 1936). While living in Brussels, Mesens was also a frequent contributor to and editor and publisher of numerous Surrealist pamphlets and journals that appeared in Belgium and France.
Through the New Burlington Galleries exhibition, Mesens gained entrance to British modernist circles, through which he met Roland Penrose and Anton Zwemmer. In 1937 he organized an exhibition of work by Joan Miró at the Zwemmer Gallery. That same year, he lent several Picassos from his own collection to the gallery.
Mesens relocated to London in 1938 and became one of the directors, along with Penrose, Zwemmer, and Peter Watson, of the London Gallery as well as editor-in-chief of the London Gallery Bulletin (1938–40). Under Mesens leadership, the gallery became the center of the Surrealist movement in Great Britain, with exhibitions that featured Cubist works, including a show of collages (May–June 1938) by Picasso and a survey of Picasso works in English collections (May 1939). In March 1947, together with Robert Melville, Mesens organized The Cubist Spirit in Its Time, which covered the trajectory of the movement from 1908 to 1929. The accompanying catalogue included texts by Guillaume Apollinaire and André Breton. After the London Gallery closed in 1951, Mesens worked as an independent curator, organizing shows for the Knokke Casino on the Belgian coast, including a Picasso retrospective (July 1950). His primary focus, however, was his own artistic work, particularly his preferred medium, collage. He showed his pieces internationally in group and solo exhibitions.