Born in London the year after the Great Exhibition, which brought grand international displays of fine art to London, Clausen was a British artist with a truly international scope. After studying at South Kensington School of Art on a two-year scholarship, Clausen decided to further his training at the Antwerp Academy. Whilst in the Netherlands he travelled along the coast, making studies in the fishing villages on his way. At this time Clausen also embarked on his first forays to Paris and the influence of French art took root in his practice, in particular the work of Jules Bastien-Lepage.
Clausen's early work, in particular the paintings of agricultural workers in Hertfordshire in 1880s, can be found in many museums around Britain and abroad. They are characterized by robust painterly qualities which they share with the best work of his contemporaries of the Glasgow and the Newlyn Schools. Unlike many of those artists however he continued to produce paintings of great distinction well into the twentieth century. He was a founder-member of the New English Art Club and was committed to reforming the selection process of the Royal Academy. He became Professor of Painting at the Royal Academy Schools, where his lectures were so popular that they were instantly published. He was knighted for his services to the arts in 1927.
Clausen was an artist of unusual integrity and singleness of purpose. At no time in his career of sixty years did he settle into a formula and produce what he knew to be popular. Although born in London, the son of a Danish sculptor and decorator, he identified closely with the rural communities of the countryside to the north of London. Perhaps because of his father's nationality, he was outward-looking from the start of his career and open to Continental influences. However the famous realist paintings of the early years are recognizably individual despite their indebtedness to Millet and Bastien Lepage. From the 1890s his palette became more colourful and forms are diffused by light in a distinctive type of British Impressionism. It was this insatiable fascination with the influence of light on form and structure that kept Clausen at his easel and which he passed on to his students in his celebrated lectures at The Royal Academy Schools.