On 5 August 2013, two people shared one hamburger in front of 200 journalists. It had taken two years to make and cost €250,000, a bill paid by the Google co-founder Sergey Brin. The man behind it, Mark Post, a vascular physiologist at Maastricht University in the Netherlands, lifted a steel cloche on a bare London soundstage to reveal a wet, reddish patty weighing 140 grams. The method was as unusual as the price.

Post's team had taken stem cells from the shoulder muscle of a living cow and fed them in plastic containers with foetal bovine serum, a nutrient liquid derived from cow foetuses. The cells multiplied into roughly 20,000 strands of muscle tissue, which were pressed together into a single patty. A Cornish chef, Richard McGeown, fried it in sunflower oil and butter for the two volunteer tasters, the American food writer Josh Schonwald and the Austrian nutrition scientist Hanni Rützler. When they cut into it, it did not bleed.

The stakes, Post argued, extended far beyond one lunch. Raising cattle consumes vast areas of land, enormous quantities of water and feed grown at a high environmental cost. He expected global demand for meat to outstrip what conventional farming could supply, which would make food systems unsustainable, from Brazilian pastures to the feedlots of the American Midwest. Cultivated beef, he suggested, could cut greenhouse-gas emissions without asking billions of people to give up red meat.