A batch of meat labeled 'pure beef' was found to contain three horse ID microchips, a court has heard.
Subsequent tests of the meat showed it contained a quantity of horsemeat described as 'significant'.
London-based businessman Andronicos Sideras is accused of 'bulking out' the 'beef' with 30,000kg of horsemeat in order to sell it to be used for ready meals and burgers.
This alleged fraud came months before the horsemeat scandal in 2013 that saw thousands of products pulled from supermarkets.
During the first day of Sideras' trial at Inner London Crown Court on July 5, prosecutor Jonathan Polnay told jurors: "It will be apparent that for the fraud to work it needed someone to carry out the physical mixing of the meats.
"It needed someone to fix the documents, to make them look genuine. That key role was taken by this defendant."
A type of horse meat called 'trim' was HorsHorse ID chips were found in the 'beef'
According to the prosecution, Danish firm Flexifoods bought horsemeat (a type called 'trim') from European suppliers. It was delivered to Sideras at his company Dinos & Sons, and he would then mix it with the beef, and create false paperwork.
Polnay said: "Dinos would create false paperwork and labels to make it look like all the meat being supplied was beef."
This could now be sold for extra profit.
Polnay claimed that Flexifood would then sell the meat mix to an Irish meat trader called McAdam's - who would then make products for a 'range of well-known companies'.
The jury was told that Flexifoods owner Ulrik Nielsen and his colleague Alex Beech - who were first arrested in 2013 - have already admitted their part in the crime.
The discovery was made when two orders were mixed up.
Prosecutor Polnay said: "It is these two orders which led to the unravelling of the conspiracy and shine a light as to what was actually going on."
Sideras was found to be in possession of paperwork (at his store) which said the 'horsebeef' was pure beef.
Mr Polnay said: "This case, stripped to its essentials, is very straightforward. It is about lying to people and deceiving people to make money.
"Or to be more precise – to make more money. Like most, if not all, offences of dishonesty, it was motivated by greed."
Sideras denies conspiracy to defraud. The trial continues.