A plot to pass off horsemeat as beef unravelled when horse identification chips were found in the meat in a surprise inspection, a court has been told.
It is alleged that businessman Andronicos Sideras, 55, one of the owners of meat company and sausage manufacturer Dinos & Sons, had mixed up the meats before they were passed on to other firms.
It was discovered after a surprise inspection in September 2012 which was only triggered after the wrong size of shipment had been sent to a company called Rangeland, Inner London Crown Court was told.
Prosecutor Jonathan Polnay said alarm bells were raised after Dinos "messed things up" when assembling an order that was to go out at the same time as another shipment.
Dino's blundered because one of the orders had been straightforward and was supposed to go in and out without any mixing. Mr Polnay said Sideras was supposed to mix Irish horsemeat with beef from two companies before sending it on to another firm.
The other order of Polish horsebeef was supposed to be sent directly to Rangeland. The shipment that was eventually sent to Rangeland was the wrong size and was sent to a store in Newry, Northern Ireland, where the surprise inspection was carried out.
Mr Polnay said: "He messed up and ended up mixing the loads together."
It is claimed it was part of a plot in which Sideras allegedly mixed the meats before they were sold on to manufacturers making products for "a vast range of well-known companies."
One of the loads, containing 12 pallets of product, ended up in a store in Newry, Northern Ireland, where an environmental health officer carried out a surprise inspection. The 12 pallets were analysed and four of them contained horse.
Mr Polnay said "some of them were found to contain significant amounts of horsemeat, roughly about a third contained horse."
Sideras's fingerprints were found on "fake" labels, Mr Polnay said. He added: "The final piece of the jigsaw is that when the meat was analysed, three horse ID chips were found in some of it."
These chips, which were roughly the size of a 1cm grain of rice, included two which were Polish and one that was from Ireland.
Sideras is said to have fabricated labels and paperwork to make the mixed meat appear like pure beef. Sideras, of Southgate, north London, denies one count of conspiracy to defraud between January 1 and November 30 2012.
It is alleged that a Danish owned company called Flexi Foods would buy horsemeat and beef from suppliers across Europe and have it delivered to Dinos & Sons in Tottenham, north London.
The meat was a type of cut called trim, considered the second-best part of the animal, generally used to make minced meat but commonly stored in frozen blocks, the court heard.
Mr Polnay said: "This was a fraud that simply could not have worked or taken place without the connivance of Sideras.
"Who else could have mixed the horse and beef together in the way it happened in this case?
"The meticulous records kept by FlexiFoods caused their undoing and what the defendant was up to. They also provide compelling evidence of the guilt of this defendant."
Mr Polnay previously told the court there is "no dispute" that the fraud was taking place, but that the jury must decide if Sideras was involved.
He told the court that two men, Ulrik Nielsen, 58, the owner of FlexiFoods, and his "right-hand man", Alex Beech, 44, have already pleaded guilty to the same charge.
The hearing was adjourned until Tuesday at 2pm.