Electronics industry in London

EMI Group Limited (formerly EMI Group plc until 2007; originally an initialism for Electric and Musical Industries, also referred to as EMI Records or simply EMI) was a British transnational conglomerate founded in March 1931 in London. At the time of its acquisition by Universal Music in 2012, it was the fourth largest business group and record label conglomerate in the music industry, and was one of the "Big Four" record companies (later the "Big Three"). Its labels included EMI Records, Parlophone, Virgin Records, and Capitol Records. Following EMI's breakup, most were acquired by Universal

The Plessey Company plc was a British electronics, defence and telecommunications company. It originated in 1917, growing and diversifying into electronics. It expanded after World War II by acquisition of companies and formed overseas companies. It was listed on the London Stock Exchange and was a constituent of the FTSE 100 Index. In 1989, it was taken over by a consortium formed by GEC and Siemens which split the assets of the Plessey group.

Racal Electronics plc was a British electronics company that was founded in 1950. Listed on the London Stock Exchange and once a constituent of the FTSE 100 Index, Racal was a diversified company, offering products including voice recorders and data recorders, point of sale terminals, laboratory instruments and military electronics, including radio and radar. At its height, Racal was the third largest British electronics firm; it operated worldwide and employed over 30,000 people. £1,000 invested in Racal in 1961 would have been worth £14.5million in 2000.

thumb|upright|A Mullard TDD4 valve. The gold spray coating served no purpose other than to hide the blackened interior, as Mullard valves were still manufactured using the azide process, long abandoned by other makers. upright|thumb|A Mullard EL34 power pentode thumb|An EL84 valve made in Russia in the 21st century