Former champion jockey Kieren Fallon and two other riders deliberately lost races as part of a betting conspiracy, an Old Bailey jury has been told.
Irish-based Fallon is a six times champion jockey
The trio agreed to make horses lose in 27 races from 2002 to 2004, but actually won six, prosecutors said.
The charges amounted to a serious fraud which "undermines the integrity of the sport", Jonathan Caplan QC said.
Six defendants deny conspiracy to defraud customers of the internet betting exchange Betfair.
The scheme helped a syndicate organised by businessman Miles Rodgers to defraud customers of Betfair, jurors heard.
Mr Caplan said Mr Rodgers, from Silkstone, South Yorkshire, was the "prime mover" of the conspiracy and stood to gain the most from it.
He said Mr Rodgers passed on instructions to jockeys Darren Williams and Fergal Lynch by mobile phone, but used intermediaries to contact Mr Fallon, who was living near Newmarket, Cambridgeshire at the time.
Kieren Fallon, 42, from Tipperary, Irish Republic
Fergal Lynch, 29, from Boroughbridge, N Yorkshire
Darren Williams, 29, from Leyburn, N Yorkshire
Shaun Lynch, 37, from Londonderry, N Ireland
Miles Rodgers, 38, from Silkstone, S Yorkshire (pictured)
Philip Sherkle, 42, from Tamworth, Staffs
Mr Caplan said: "The defendants in this case did not fix races to ensure a horse won. On the contrary, they fixed the races to ensure that the horses in question lost.
"The object of the conspiracy was to wager large amounts of money on a particular horse to lose in each of those races whilst knowing that the jockey was prepared, if necessary, to cheat by stopping his horse."
Mr Lynch's brother Shaun Lynch, 37, of Londonderry, Northern Ireland, and Philip Sherkle, 42, of Tamworth, Staffordshire, have also pleaded not guilty to being involved in the conspiracy.
Mr Caplan said there were various, often "very subtle" ways of making a horse lose, including holding it back or deliberately riding into "a wall of other horses" to impede its progress.
"The plan was not and could not be foolproof because you could not always stop the horse if in the particular circumstances it would look too obvious," he said.
"A horse race is a dynamic event and anything could happen - but the plan worked most of the time."
The prosecution say that shortly after phone calls from the jockeys, Mr Rodgers would place large bets "or lay bets to achieve a small return by comparison".
Bets were usually more than £100,000 to win about £20,000, but some were £60,000 to win about £4,000, Mr Caplan said.
These bets usually amounted to just over 50% of the Betfair market in a particular race, he said.
And in total, £2.2m was laid by Mr Rodgers' Betfair accounts between December 2002 and the end of August 2004, he added.
This period covered 27 races, of which Mr Fallon rode in 17.
Mr Caplan said Mr Fallon "won for the conspirators 12 times by losing, but he lost for them five times by winning".
The defendants deny any wrongdoing and say they phoned each other before races to pass on tips or betting information.
"Fallon's position appears to be that he would discuss the prospects of his own rides with Fergal and Shaun Lynch, but was completely unaware if they passed this information on to Rodgers," Mr Caplan said.
But, Mr Caplan claimed, there was "something far more sinister and unlawful going on".
Mr Fallon, who now lives in Tipperary in the Irish Republic, has won six champion jockey titles in the UK and on Sunday he won France's biggest races, the Prix de l'Arc de Triomphe.
"There can be no question that he is regarded as being one of the leading jockeys in the world," Mr Caplan said.
The trial continues.