The gang was recruited by a former antiques dealer serving a life sentence for murder who had collected the horns before it became illegal to sell them, King's Lynn Crown Court was told.
Wilfred Bull, 63, wanted to sell the 127 horns in preparation for his release from prison and called in a "lady friend", Carol Scotchford-Hughes, who brought in another couple, David Eley and Elaine Arscott.
But Royal Society for the Prevention of Cruelty to Animals officers and police were tipped off after Ms Arscott, using a false name, phoned the London Stock Exchange to inquire about selling them.
The unsuspecting gang held several meetings - one of which was bugged - with the undercover officers at a hotel in Cambridge to talk about the deal. RSPCA inspector Alan Fisher told the court he was in regular contact with the gang in 1996 to make the arrangements.
Mr Fisher told the court Mr Eley referred to the rhino horns as "antique chairs" for security reasons, unaware the conversation was bugged, and the deal was fixed for 3 September 1996.
The gang were arrested after police raided a store in west London where the horns were being kept.
The court had earlier been told that rhinos were an endangered species and it was illegal to trade in them or their horn. "If you kill the trade, it reduces the incentive for destroying the animals," said John Farmer, opening the case for the prosecution.
The horn is seen as an aphrodisiac in the Far East and fetches pounds 12,000 per kilogram, Mr Farmer told the court.
Bull, who was jailed at the Old Bailey in 1986 for the murder of his wife Patsy a year earlier, contacted a legal executive, Paul Rexstrew, from his prison cell to arrange the financial transaction and launder the money, the jury was told.
Mr Rexstrew, of Wimbledon, south-west London, denies conspiracy to sell rhino horns, claiming he knew they were dealing with art treasures and animal trophies but did not know it was rhino horn.
The jury has been told that Carol Scotchford-Hughes ofWillingham, Cambridgeshire, and Elaine Arscott and David Eley, both of Great Shelford, Cambridgeshire, have pleaded guilty to the charge. Bull has pleaded guilty to the charge under the Control of Trade in Endangered Species (Enforcement Regulations) Act 1985.
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