Would you put on a helmet to walk to the shops? Probably not. So why should I put on a helmet to ride my bike down the road?
Now I accept there is a rather different order of risk involved in those two activities. But since almost nothing we do is entirely without risk – remember, most accidents happen in the home – all we're really arguing about here is a matter of degree.
I don't know what the odds are of being knocked off my bike every time I ride to work across London, but I do know that when, helmetless, I set off, I am backing my ability to negotiate my way safely. I much prefer not to have the encumbrance of a helmet. I believe – and research supports this – that motorists are more aware of the cyclist whose face and head are fully visible. I don't want the terms on which I ride dictated to me, and I am happy to take responsibility for myself.
In my experience, the people most concerned about (and disapproving of) those who choose not to wear a helmet are invariably non-cyclists. Either they think that to cycle without one you must have a death wish (which I certainly don't), or they are the kind of motorist who thinks cyclists, helmeted or not, have no place on the road. Naturally I wouldn't dare speculate on whether Justice Griffith Williams falls into either or both of those categories.
In London there is a strong helmet-wearing culture, and that's fine. But in Paris, for example, you hardly ever see a cyclist in a helmet. Parisian cyclists, it seems, feel safe on their bikes,and I feel safe on mine. If I didn't, I wouldn't cycle at all.