I’VE BEEN MAKING a radio series about departed heroes. I choose the living and my studio guest chooses the dead. And the most mysterious of our ghostly invitees has been an obscure 19th-century Hungarian doctor, Ignác Semmelweis, patron saint of “now wash your hands”. Frances Cairncross, president of the British Society for the Advancement of Science, chose him. Her hero, practising in the maternity wards of a Viennese teaching hospital, hit upon the cause of the deaths from “childbed fever” of hundreds of thousands of postnatal mothers across Europe and America. Simple observation told him they were killed by their doctors, who carried the infection on their hands from one woman in labour to another. When doctors washed their hands between patients, deaths plummeted. It was that simple.

But a conservative medical profession refused to accept they could be killing women. Semmelweis lashed out at his colleagues as murderers. He was shunned. He died in a lunatic asylum. It was years before his theory took hold, yet the truth had been staring his era in the face.

Making the programme, I started to wonder what obvious truths stare our own era in the face. Every generation tumbles to something their grandfathers just couldn’t see, and exclaimed: “Surely it was obvious?” Could ours be the first age to overlook nothing? Or what no-brainer might be staring us in the face?

I DO HAVE one candidate, though rather trivial. In 1996 I wrote a weekly humorous column on these pages. Returning from an expedition where we could hardly wash for weeks, I reported that my hair had become progressively greasier, and then — to my surprise — begun to get less greasy again. I recorded my hunch that it might not be necessary to wash your hair with shampoo, soap or any kind of de-greasant. Pointing out that cats and monkeys never use shampoo yet do not seem to suffer from oily fur, I suggested that if humans, too, stopped stripping our hair of natural oils, our scalps might stop pumping them out. I promised readers I would try this. Maybe they thought I was joking.

Today, after ten years of washing my hair with fresh, warm water alone — ten years during which no kind of de-greasant has touched my scalp — I can report back. Readers, if only you could all run your fingers through my hair: as light and fluffy as a kitten’s coat. And (to answer your unspoken question) not at all smelly — snuffle your noses in it, do — because I rinse my hair daily under the shower. Do you soap up your kneecaps every day? No. Are they oily or smelly? I doubt it. Exposed to light and air, human skin and hair find their own balance, the oil-glands secreting just enough to protect. It is our habit of stripping this viciously from our scalps that panics the glands into overproduction — that is why your first few weeks will be an uncomfortably greasy time. But persist, and you’ll come out the other side with less dandruff than when you were shampooing, and less greasy hair than the second day after you quit.

Think of the money, think of the pollution, our nation could save. No wonder everyone’s going bald. One day I shall be hailed as a lonely prophet of the nonsense of shampoo.

AND HERE’s another lonely prophet who noticed the blindingly obvious: the late Sir Robin Day, then aged 31 and a junior radio producer, writing a memo to BBC senior management in 1955 suggesting that at breakfast the Home and Light Services should offer more than light music, No, No, Nanette and readings from Ezekiel. “I therefore suggest a new daily morning programme . . . [giving] intelligent, pithy comment . . . on things people may not yet have read about in their morning papers.” Day concluded that if his proposal was adopted, “I am sure we would look back to the present morning programmes with the same incredulity with which we now regard pre-1939 days when there was nothing, not even a news bulletin, until mid-morning”.

The whippersnapper’s idea got short shrift from the Controller of the Home Service. He doubted there was any “public demand for this sort of thing in the morning”, and turned it down flat. Later the Today programme was born. It was staring them in the face — wasn’t it?

Times Recommends

• In the real world, the public sector must pay
• Playing politics in a land of double Dutch
• Be like the plinth people: not set in stone