Border Force officers unearthed £3 million worth of cannabis in a lorry containing crates of parsley.
The 600kg haul was discovered inside a Spanish-registered vehicle at the Port of Dover on Monday, the Home Office said.
A Spanish man was arrested and the investigation was passed on to the National Crime Agency (NCA).
He was later released under investigation while NCA inquiries continue.
Chris Philp, minister for immigration compliance and the courts, said: “The professionalism and vigilance of Border Force officers has prevented a significant quantity of illegal drugs entering the UK and ending up on our streets.
“Working with the National Crime Agency and other law enforcement partners, we will continue to tackle drug smuggling and bring those responsible to justice.”
