William S. Verrells, a schoolmaster and freelance journalist from Southend-on-Sea, wrote an article in a local newspaper asking if it was possible to power a radio set from the mains electricity supply rather than batteries. Cole saw a possible business opportunity and set about building his battery eliminator, which he later demonstrated to Verrells. Suitably impressed, Verrells joined Cole in a business venture, with Cole manufacturing the battery eliminators, and Verrells marketing them. In 1926 a private company E.K. Cole Ltd was formed with Verrells as chairman and Cole as vice-chairman. With the extra funding that was raised, the company set up a new factory at Leigh-on-Sea in 1927. After further expansion E.K. Cole Ltd became a public limited company in 1930, and moved to a spacious new factory at Southend-on-Sea. The company also began to concentrate on the manufacture of mains powered radios rather than battery eliminators which were becoming obsolete. Another important development for the company was the introduction of bakelite cabinets for its radios. Initially these cabinets were made for the company in Germany by AEG, however the introduction of high import duties on the cabinets in 1931, forced Ekco to establish its own bakelite moulding shop adjacent to its Southend-on-Sea works. The round bakelite radio cabinets for which the company became famous, were designed by the noted Canadian architect and industrial designer Wells Coates.
In 1935 Ekco made a substantial investment in Scophony Limited, the developers of the ingenious Scophony projection television system. Although the Scophony system showed great promise, its development was halted by the Second World War, and not resumed postwar.
Malmesbury specialised in the top secret development and production of the new radar systems as part of the "Western Development Unit". Radar equipment produced at Malmesbury during the war included, the AI Mark IV and AI Mark VIII air interception radars, and the ASV Mark II air to surface vessel radar.
In addition to radar equipment, Ekco also manufactured the ubiquitous R1155 and T1154 aircraft radios at its Aylesbury shadow factory. Ekco carried out extensive development work on both units before putting them into production, significantly improving on the original Marconi design. The R1155 and T1154 were also produced by Marconi, Plessey, and EMI. The company also manufactured the Wireless Set No. 19 tank radio at Woking, it was a Pye designed set made by several other British and American companies. In 1942 Ekco began production of its Wireless Set No. 46 portable man-pack radio, large numbers of these were made at the company's Woking and Southend-on-Sea factories.
By 1973 Ekco had been absorbed into a conglomerate and its products were mostly rebadged Pyes. Later the Ekco name was dropped entirely.