The narks would say that, if you injure your head in a bike crash, you will be levying an impost on the public purse through your NHS treatment. A lot the narks know. If you come off a bike at more than 20 mph and land on your bare bonce, the resulting mess may distress onlookers and the paramedics who are summoned to the scene; but you're unlikely to be troubling other professionals apart from the mortician and the undertaker. Their services are not usually covered by the NHS. If you are wearing a helmet and you clout your head in a crash, however, you might find yourself (if you can find yourself at all) in quadriplegics’ traction or in ICU for decades. Good luck.