Penicillin is regarded as the prime example of the failure of British scientists to develop their inventions and to lose them to American commercial exploitation. However, British efforts to commercialize penicillin were extensive, and involved collaboration between major pharmaceutical corporations. This detailed analysis shows what work was done during World War II, and why the British were less successful in scaling up laboratory procedures sufficiently. This reflects as much upon attitudes towards the use of science in industry as upon financial opportunity.