Police discovered an enormous stash of cocaine in three safes hidden behind a false wall in a lock-up building.
Officers from the Metropolitan Police's central task force stopped a 26-year-old man in Goffs Oak, Hertfordshire, yesterday afternoon, after he left the building in St James's Road.
They found he had a kilogram of cocaine on him, and the man was arrested on suspicion of possession with intent to supply class A drugs.
Searching the premises officers found three safes behind a false wall, which contained 29kg of cocaine, scales and other drugs paraphernalia.
The man was taken to a north London police station, where he remains in custody.
Detective Inspector Colin Stephenson of the central task force said: "This is another example of good detective work by my team, which has prevented a huge amount of cocaine destined for London from reaching the streets.
"My message to those involved in the drugs trade is that we will pursue you relentlessly and make you face the consequences of your actions."