J. J. Connington 
Nordenholt’s Million [PDF ebook] 

As a bacteria threatens to wipe out humankind, a plutocrat sets himself up as the benignant dictator of a survivalist colony.In this novel originally published in 1923, as denitrifying bacteria inimical to plant growth spreads around the world, toppling civilizations and threatening to wipe out humankind, the British plutocrat Nordenholt sets himself up as the benignant dictator of a ruthlessly efficient, entirely undemocratic, survivalist colony established in Scotland’s Clyde Valley. Discovering just how far their employer is willing to go in his effort to spare one million lives, Jack Flint, the colony’s director of operations, and Elsa Huntingtower, Nordenholt’s personal assistant, are forced to grapple with the question of whether a noble end justifies dastardly means.