As the gang's drug-filled lorry jammed against the roof in the northbound lane, their accomplices returned to see what was wrong and their car became trapped in the southbound lane.
The lorry became stuck just as the evening rush hour began, the jams spread and large areas of East London were gridlocked for several hours.
The scene was recounted at Southwark Crown Court in London yesterday. While presenting happy Customs officials with a pounds 7.28m high-quality haul, the "cock-up" factor - as the prosecution called it - had the lorry firmly blocking the entrance to one tunnel. Their accomplices' car ended up slewed across the carriageway, jammed between a wall and a Customs surveillance vehicle.
The jury found gang leader Hamid Shamsollahi, 38, an Amsterdam-based businessman from Iran, guilty of one count of smuggling. The lorry driver, Mustafa Karinca, 50, from Istanbul, Turkey, was convicted on a similar charge.
The two men and another gang member, Turkish-born Korkut Eris, 40, a minicab driver from Hornsey Road, Holloway, north London, who admitted the charge, will be sentenced on Monday.
A fourth, Feretin Eren, 23, a Turkish national from Edmonton, north London, was found not guilty.
The five-week trial heard that to begin with the men's meticulous planning paid off. The massive articulated lorry, bought months earlier at auction, was fitted with a false fuel tank. Inside was a secret compartment used to hide the 65.84- kilogram consignment, which Karinca is believed to have collected in Turkey.
It was so well installed that Customs officials at Dover failed to detect anything wrong when he arrived by cross-Channel ferry from Zeebrugge, Belgium, in February this year.
Confident everything was going according to plan, he then drove the lorry and its illicit load to Medway services on the M2 in Kent, where he settled down for the night. But Customs and Excise's National Investigation Service had been tipped off.
Then next day, Shamsollahi and Eris were followed as they drove down from London to rendezvous with Karinca. Once there, they spent the next two hours trying hard not to recognise one another in the motorway stop's Burger King.
As soon as Eren arrived, they suddenly seemed to discover they knew one another after all, and shortly afterwards left the service station in convoy.
Forty-five minutes later the mathematical impossibility of trying to fit the over-tall lorry into the 14ft 3in high Blackwall Tunnel triggered electronic warnings and the end of the gang's short but memorable criminal career.Reuse content