He studied architecture at Gloucestershire College of Art in the 1960s. In 1970, he moved to Milan, where he began working with renowned designer Ettore Sottsass and the Italian company Olivetti. In 1979, Sowden established his own design and product development studio, SowdenDesign. He was a founding member of the Memphis Group in 1981, a design movement that significantly influenced the aesthetics of the 1980s. In 2010, he founded his own brand, SOWDEN.

Throughout his career, Sowden has collaborated with various companies, including Olivetti, Alessi, Bodum, Guzzini, Lorenz, Rancilio, Steelcase, Swatch, Segis, Memphis, IPM, Moulinex, Telecom Italia, Tefal, and Pyrex. His work is held in the collections of several prestigious museums, such as the Metropolitan Museum of Art, the Brooklyn Museum, the Cooper Hewitt Museum in New York, the Museum Boijmans Van Beuningen in Rotterdam, and the Victoria and Albert Museum in London.

In 1991, Sowden received the Compasso d'Oro Award for design excellence for his work on Olivetti's Fax OFX420