Mohammed Hussain, from Sheffield, was stopped after getting off a ferry in Dover in September last year when officials began to ask where he was travelling from.
Hussain, of Uttley Drive, initially told Border Force officers he had been to Frankfurt and stayed in a Holiday Inn in the preceding four days.
But the 29-year-old was unable to provide any details about his stay, and soon switched his story saying instead that he had been in Amsterdam.
A later search uncovered 16 kilos of cocaine and heroin in taped packages which had been hidden in all four door panels of the car.
Small amounts of cannabis were also found in the car following further searches.
The cocaine and heroin would have been worth around £1 million if sold on the streets of the UK.
Hussain was subsequently charged with attempting to import class A drugs and convicted yesterday (14 June) following a four-day trial at Canterbury Crown Court.
NCA Branch Commander Martin Grace said: “Officers were immediately suspicious when Hussain seemed to have forgotten where he had spent the days leading up to his arrest. His story just wasn’t plausible.
“As it turned out his car was carrying a lethal cargo of class A drugs, the kind distributed by county lines gangs and other exploitative criminal networks throughout the UK.
“By continuing to work with our partners like Border Force, we will bring the full force of the law down on drugs smugglers and disrupt the organised criminals pulling the strings behind them.”
Hussain will be sentenced at a later date.