©Wellcome Library, London

In 1940, after the evacuation of the British Expeditionary Force from the French Channel port of Dunkirk, it was feared that a German invasion of Britain was imminent. Florey, Chain, and their colleagues used to smear spores of penicillin culture on the lining of their coats in the hope that if Oxford fell to the enemy, at least one of them might survive to carry on the work. American pharmaceutical companies, Merck, Squibb and Pfizer produced most of the wartime penicillin whilst British companies, ICI, Burroughs Wellcome and Glaxo participated from 1943. In 1996, an early sample of penicillin was sold by auction at Sotheby's for £20,000. In this photograph showing the inoculation room at ......, milk bottles in tiers are ‘sown' with Penicillium spores and then carried to incubators.