Rather like Public Eye, this series had begun life at ABC-TV, first as a play in the famous Armchair Theatre strand (04/02/1967), and then a series of six episodes in 1968. When Thames picked up the franchise, three more series were made from 1969-72. Edward Woodward stars as the secret serviceman Callan, supported by Russell Hunter as his grass, Lonely, and William Squire as his commander.