Ferranti Ltd began working on computers in 1947, and by 1949 had established a Computer Group within the company. The Group worked with academic researchers, notably at the Universities of Manchester and Cambridge, and delivered the world's first commercially available computer in 1951: the Ferranti Mark 1. The collaboration with Manchester went on to produce the Ferranti Mercury and Atlas, whilst work with Cambridge led to the Atlas 2 or Titan. In 1953-1955 Ferranti set up a sales and development centre in central London, at Portland Place, in order to encourage a market for their products. A Pegasus computer was built on site. Other machines developed in the 1950s included the Pegasus II and Perseus models, as well as the Orion models. These machines were found to be useful in the aerospace industry and for nuclear research. From 1958-1962 Ferranti attempted to dramatically improve performance with a completely new design of computer: the Atlas. Background research was carried out at the University of Manchester and was known as the MUSE project. In 1963 the computer department was sold to International Computers and Tabulators. However, Ferranti continued to produce computers for the industrial sector through the Ferranti-Packard division, and work continued at the company's Bracknell, Wythenshawe and Cheadle Heath sites in industrial computing, automation and military computing. In the 1960s and 1970s the company developed its Argus models. Ferranti Computer Systems Ltd was formed in 1977 to bring together Ferranti’s computing divisions at Bracknell (digital systems), Wythenshawe (automation), and Cheadle Heath (military systems). The new company had a workforce of 4,400 and a £30 million pound annual turnover. The company was successful throughout the late 1970s and into the 1980s. Ferranti Computer Systems developed and manufactured control, monitoring and communication systems for industrial processes such as oil and gas extraction, public utilities, data communications networks and road transport. They were also involved in information systems including for air transport, providing data processing terminals, office systems, industrial and commercial local area networks. The company also supplied equipment to end users. As well as being active in the UK, by 1988 the company had subsidiaries in Australia, West Germany, Belgium and America. In 1994 Ferranti entered receivership. The computing division was sold to a division of Thomson-CSF, known as SYSECA. The company adopted the name Ferranti-SYSECA, which fell out of use around 1996. Ferranti Computer Systems merged with Thales UK in 2000, whereupon all operations were moved to Cheadle Heath on the outskirts of Manchester.

Ferranti Thomson Sonar Systems (FTSS) was established in 1990 by the merger of the sonar systems businesses of Thomson-CSF and Ferranti, initially under the name Thomson Marconi Sonar (TMS). The head office of FTSS was at Cheadle Heath, Stockport, with subsidiary sites in Church Crookham, Hampshire, Weymouth, Dorset, Bridlington, Yorkshire and Rochester. GEC acquired Ferranti's share of the business in 1995 to form Thomson Marconi Sonar. In 1999 BAe Systems was formed out of a merger of GEC's defence business Marconi Electronic Systems and British Aerospace, with the new company acquiring Marconi's share in TMS. In 2001 Thales acquired BAE Systems' share in Thomson Marconi Sonar (TMS), and Thomson Marconi Sonar was renamed Thales Underwater Systems.

Maritime International Ltd was a publishing company established in 1971 and based in London. The business produced consumer and business journals and periodicals, including 'Navy International' magazine, previously the Navy League's own journal. The business was wound up in 1996, with Navy International moving publisher to Coulsden, and continuing to be published as Jane's Navy International.