Today is World Blood Donation Day - a good time to start giving blood if you're eligible and don't already. However, the history of blood donation actually begins in seventeenth-century London.
Once William Harvey had published his account of the circulation of the blood in 1628, other eminent people became interested in this area. Sir Christopher Wren, better known as an architect, was the first person to inject fluids into animals' bloodstreams; in 1666, Richard Lower carried out blood transfusions between animals. The following year, he transfused sheep's blood into one Arthur Coga at the Royal Society, apparently without ill effects. However, there was outcry over such experiments in Britain and France and the work was not pursued (perhaps fortunately!).
Human blood transfusions only began again in the early nineteenth century with the work of London obstetrician James Blundell, but lack of knowledge about blood groups meant that they often weren't successful. When Dr Karl Landsteiner identified the four main groups, transfusions became truly possible just in time for the First World War.
The British Red Cross began organising donations in 1921. Today, the national service is well-developed but still struggles to find enough donors. If you're interested in donating, there's all the information you could want here - and don't forget that as well as saving lives, you also get free tea and biscuits!