John Johnstone was born April 28, 1734, the youngest son of Sir James Johnstone, Bt. and Barbara Johnstone, of Westerhall. As a young man, he served in the East India Company, as Commander of the artillary at the famous battle of Plassey, 23 June 1757, and on the Council of Bengal from 1761 to 1765. An unscrupulous businessman, he returned home in disgrace, but with a vast fortune. He purchased Alva and other large estates in Scotland, and was a Member of Parliament for Dysart Burghs from 1774 to 1780, voting with the Opposition and adopting a consistently pro-American stance. In 1765, he married Elizabeth Caroline, daughter of Col. Keene; they had a son and a daughter. Johnstone died December 10, 1795.