British new car sales fell by roughly 20 percent in September, according to preliminary data from an industry body on Thursday, as carmakers struggled to adjust to stricter emissions standards. On Sept. 1, Worldwide Harmonized Light Vehicle Test Procedure (WLTP) came into force in the European Union, which led some brands to incentivize sales in August, pulling forward demand. Certain automakers have been unable to recertify all of their models in time, also disrupting sales in September, which is a key selling month in Britain as one of only two occasions when a new license plate series is introduced. Europe’s second-largest car market has also been hit by double-digit drops in diesel sales due to uncertainty over government policy and a subsequent levy hike, the Society of Motor Manufacturers and Traders (SMMT) has previously said. Since hitting record highs in 2015 and 2016, car registrations have fallen in Britain, also impacted by Britain’s imminent departure from the European Union, the SMMT has said. Volumes were down among both private and business buyers, according to the initial data. The industry body will publish final figures at 0800 GMT on Thursday.