Nearly 519,000 new cars were snapped up in March, the highest monthly total this century, new figures show.
According to the Society of Motor Manufacturers and Traders (SMMT), last month's sales were 5.3% up on March 2015.
The total is the highest since the current system of twice-yearly number plate changes began in 1999.
The 31 days after the latest number plate change on March 1 saw 518,707 new cars registered.
The number of cars sold to private motorists was 3.8% up on March 2015, while the number sold for fleet use jumped by 6%.
Sales of both petrol and diesel cars grew by nearly 5% year-on-year, while those of alternatively-fuelled ones soared by 21.5%.
Mike Hawes is the SMMT's chief executive. He says the growth in March completes a strong first quarter for the industry.
He is predicting that consumer demand will remain high through the rest of the year but warns that political or economic uncertainty could have an impact.
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