Regardless, he was General Secretary of the Miners’ Federation of Great Britain from 1924 until 1931, a period that included the 1926 General Strike, about which he wrote the pamphlet "The Nine Days". This led to his becoming closely associated with the slogan, "Not a penny off the pay, not a minute on the day". He was also elected as secretary of the International Miners' Federation. Although a member of the Independent Labour Party, Cook worked closely with the Communist Party after its formation in 1920 and the National Minority Movement from 1924 to 1929. Arthur Horner, a leading South Wales Communist and mining militant described Cook's tenure as General Secretary as “a time for new ideas — an agitator, a man with a sense of adventure”. Cook died of cancer in 1931, aged 47.