As of October, it is illegal to smoke in a car in which children are travelling in England and Wales.

The ban still applies even if the windows are wide open or the air-conditioning is turned on, however convertible drivers may still smoke as long as the roof is fully down, and electronic cigarettes are not covered by the ban. Drivers will also be breaking the law if they fail to prevent passengers lighting up if anyone under 18 is in the vehicle.

Those breaking either law face a £50 fixed penalty notice fine, and can be fined separately for each, although a 17-year-old driver smoking alone in a car is not committing an offence.

Chief medical officer Professor Dame Sally Davies said: “This legislation is a landmark in protecting children from second-hand smoke. Smoking just a single cigarette in a vehicle exposes children to high levels of air pollutants and cancer-causing chemicals like arsenic, formaldehyde and tar, and people often wrongly assume that opening a window, or letting in fresh air, will lessen the damage.”