Cultivating penicillin proved difficult and the small quantities that could be produced were unstable. Fleming also believed that penicillin would not remain in the human body long enough to kill bacteria. Taken together, these facts convinced Fleming that penicillin would never be an important antibiotic for treating infections. For the next decade, penicillin remained a laboratory curiosity, until Howard Florey and a team of researchers at Oxford University demonstrated its potential life-saving properties. The researchers also discovered a method to purify penicillin and to keep it in a stable form. By 1940, clinical trials were underway and their success led to the hunt for a method to manufacture this “wonder drug.” But by then England was at war, making mass production difficult. So the question remained: how to produce penicillin on a large scale?