The Scottish microbiologist Alexander Fleming was a medical scientist who discovered penicillin, the first antibiotic.

As a boy, Fleming worked in a shipping office in London until an inheritance enabled him to study medicine at St Mary's Hospital. He was interested in microbes which caused diseases such as tetanus and gangrene, and searched for substances to combat them.

In 1928 Fleming observed that a mould which had accidentally grown in a Petri dish with a culture of bacteria had killed the germs around it. He called the active substance in the mould ‘penicillin’.

Penicillin became a life-saver in the Second World War when Howard Walter Florey and Ernst Boris Chain came across penicillin in their search for antibiotic substances - research which finally enabled the large-scale production of the antibiotic. Fleming was elected Fellow of the Royal Society in 1943 and knighted in 1944. In 1945 he shared the Nobel Prize in Physiology or Medicine with Florey and Chain.