Perseus was a vacuum tube (valve) computer built by Ferranti Ltd of Great Britain. It was a development of the Ferranti Pegasus computer for large-scale data processing.[1] Perseus, which was one of Ferranti's computer systems that included Orion and Sirius,[2] was the company's first production machine marketed towards commercial users.[3] The system used the automatic checking method.[1] Two were sold, both to overseas insurance companies in 1959.[4]