In 1928, Alexander Fleming came back from a two-week holiday to find a stray mould contaminating a stack of Staphylococcus plates in his St Mary's lab, and the clear ring of dead bacteria around the fungus became the accidental start of the antibiotic era

When Alexander Fleming returned to his St Mary's lab in September 1928, a stray Penicillium mould had colonised a forgotten Staphylococcus plate — and the clear ring of dead bacteria around it opened the antibiotic era that has since saved an estimated 500 million lives.