The private papers of former British Prime Minister Harold Macmillan show his government kept secret the details of a 1957 accident at an atomic power plant that contaminated milk at about 800 farms, according to the Observer, a London newspaper. It marked the first time that full details have been revealed about the accident at the Windscale nuclear plant in northwest England. Macmillan apparently kept the information secret because he feared shaking public confidence in the industry. The Observer cited the documents as saying the accident contaminated milk with high levels of strontium 90, a deadly isotope found in radioactive fallout. The newspaper made no mention of any deaths attributed to the accident.