He painted both formal portraits, such as that of the Canadian war hero G.B. McLean, and Impressionist works such as the 1921 painting Venus in Kensington Gardens. In his Hammersmith studio Underwood set up a private art school, the Brook Green School, which he ran, intermittently, until 1938. At Brook Green, Underwood initially, concentrated on teaching printmaking with woodcutting but also began making sculptures. In 1925, with some of his past pupils, Underwood created the English Wood-Engraving Society to promote the art form. Later in his career, between 1935 and 1945 Underwood created a significant number of colour linocuts. In 1922 Underwood had his first solo exhibition at the Chenil Gallery in London. An exhibition of his sculptures was held in 1924. He also taught a life drawing class at the Royal College of Art from 1920 until 1923 when he resigned and travelled to Paris and Iceland. In 1925 he became the first contemporary artist to spend time examining the cave paintings at Altamira in Spain. Underwood spent 1926 in the United States where he published an illustrated book of verse, Animalia, illustrated some volumes by others and also painted and made engravings. In Greenwich Village he opened a life-drawing school. In 1927 he went to Mexico, spending five months travelling and studying Aztec and Mayan art forms. After returning to England in late 1928 Underwood made a number of paintings on Mexican themes, including imagined portraits of Montezuma II and Hernán Cortés, the latter holding a stone heart in front of a ruined castle. He also created several surrealist paintings, six of which were shown at the first, and only, exhibition of The Neo Society held at the Godfrey Phillips Gallery in London in May 1930. With funding from Eileen Agar, Underwood co-founded a graphical quarterly magazine, The Island, in 1931 which, despite contributions from Henry Moore, Agar, CRW Nevinson and Mahatma Gandhi was only published for four issues. From 1932 to 1934, Underwood made a series of sculptures of dancing figures including Herald of New Day, the plaster cast of which is now in the Tate collection. In 1934 he published an artistic manifesto, Art for Heaven's Sake: Notes on a Philosophy of Art. Underwood was always convinced that subject matter formed a fundamental role behind the power of both his own and primitive art, and had no belief in subject-less or purely abstract form in his