What is thicker, driver or fog?

Succinct rant follows;

Rule 211
You MUST NOT use front or rear fog lights unless visibility is seriously reduced (see Rule 201) as they dazzle other road users and can obscure your brake lights. You MUST switch them off when visibility improves.
Law RVLR regs 25 & 27

Click here for the highway code website. Rant over!