I remember a wonderful comment in one of Alistair Cooke’s Letters from America. His doctor said that there is a real medical breakthrough – a totally new drug, or a revolutionary surgical procedure – about once a generation. And yet on network television there was a medical breakthrough at 7.15 every Friday night.

I am glad to say Medical Mysteries, on BBC1 at xx on yy, will concentrate not on these hyped-up wonders of the practitioners’ skill, but rather on extraordinary cases of human resilience, persistence, and survival. The human body is so complicated that even the most brilliant doctor sometimes cannot tell what is wrong with it, nor what is going to happen, but it has immense powers of recovery, and the main job of most doctors is to assist the self-healing process.

My great hero Erasmus Darwin, Charles’s grandfather, was the victim of two fluky cases. He learned his medicine at Edinburgh, and opened a practice in Nottingham, where he had just one patient, a shoemaker who had been stabbed by another shoemaker. Unfortunately the man died; so Dr Darwin received no fee and no recommendation, but was saddled with a 100 per cent mortality rate. Not a promising start.

He began again in Lichfield, where the gods proved kinder. One of his first patients was a man who had been diagnosed as incurable, but under Darwin’s care made a full recovery; Darwin’s reputation was assured. A patient came for a consultation all the way from London – several days’ travel in the 1760s. Darwin examined him, gave his verdict, and then asked why he had come to Lichfield. Why had he not consulted the celebrated Dr Warren in London? The patient replied ‘I am Dr Warren.’

Darwin had a colleague - a boring doctor called William Withering, one of whose patients was suffering from an irregular heartbeat. Withering dismissed the man, saying there was nothing he could do, but the man went and found a gypsy healer – and was cured. Withering was amazed. He tracked down the gypsy, and discovered that the main ingredient in the healing potion was foxglove. Withering investigated, and so discovered the effect of digitalis on the heart. Even today digoxin and digitoxin are highly effective drugs in the treatment of irregular heartbeat.

So luck and miracles do play a significant part in medical practice, but do not expect a breakthrough every Friday night.