Overview (rule 226)

Highway Code Rule 226

You MUST use headlights when visibility is seriously reduced, generally when you cannot see for more than 100 metres (328 feet). You may also use front or rear fog lights but you MUST switch them off when visibility improves (see Rule 236).

Law

Section: Driving in adverse weather conditions (rules 226 to 237)
Subsection: Overview (rule 226)