The article draws up an assessment of the resources and instruments a new prime minister inherits on his or her first day in 10 Downing Street. It examines the growth in the functions that have fallen to successive prime ministers, as heads of government, over the seven decades since the end of the Second World War. It explains the very special and personal nuclear weapons responsibilities that belong to a prime minister. It touches, too, on the physical and mental strains that often afflict those who carry the office of prime minister. The article examines Jack Straw’s proposal that the United Kingdom prime minister and the collective Cabinet system over which he or she presides should be placed on a statutory basis by Parliament.