Highway code rule 114
Lighting requirements Rule 114 You MUST NOT: use any lights in a way which would dazzle or cause discomfort to other road users, including pedestrians, cyclists and horse riders use front or rear fog lights unless visibility is seriously reduced. You MUST switch them off when visibility improves to avoid dazzling other road users (see Rule 226). In stationary queues of traffic, drivers should apply the parking brake and, once the following traffic has stopped, take their foot off the footbrake to deactivate the vehicle brake lights. This will minimise glare to road users behind until the traffic moves again.