He was born in Germany and studied carpentry and furniture design in Berlin before moving to London in 1909 to work at Heals. He rose rapidly through the ranks to become design director in 1915.
During his time at Heals, Hornby designed a range of modern furniture that was highly influential in British design at the time. His pieces were often characterized by simple geometric shapes and natural materials such as wood and leather.
In 1933, Hornby left Heals to work at Harrods, where he continued to design modern, functional furniture. He was also involved in the design of the "Modern German Furniture" exhibition at Harrods in 1938, which featured pieces by contemporary German designers such as Ludwig Mies van der Rohe and Marcel Breuer.
Hornby continued to work for Harrods until his retirement in 1953. He died in 1965, leaving behind a lasting legacy in British design.