A woman allegedly pretended to be a gem expert and swapped diamonds worth 4.2 million pounds ($7.8 million) for pebbles using “sleight of hand” at a jeweller in London.
Prosecutors told a British court how Lulu Lakatos, posing as a gem expert, went to value seven diamonds at Boodles in 2016.
Ms Lakatos was allegedly representing a group of wealthy Russian buyers.
The jewellers placed the diamonds in a locked bag inside a vault waiting for the payment to be transferred from Ms Lakatos’s buyers.
The diamonds included a 20-carat heart-shaped diamond valued at more than 2.2 million pounds.
But the Boodles’ diamond expert became suspicious and opened the bag the next day.
She found seven small pebbles.
Prosecutor Philip Stott said the diamonds had been “stolen by the defendant by sleight of hand”.
“The conspiracy in which she is alleged to have played an integral and central part was one of the highest possible [in terms of] sophistication, planning, risk and reward,” he said in court.
Ms Lakatos is charged with conspiracy to steal but denies any wrongdoing.
The chairman of Boodles, Nicholas Wainwright, said in a statement that weeks before the theft he had been approached by a buyer who wanted to invest in high-value diamonds.
He agreed to the sale of the seven diamonds and met with Ms Lakatos in his shop’s basement, along with his diamond expert Emma Barton.
As soon as Mr Wainwright left the room to take a call from the alleged buyer, Ms Lakatos put the padlocked purse containing the gems in her handbag, Ms Barton told the court.
Ms Barton said she protested, but Mr Stott alleged that Ms Lakatos swapped the purse with an identical locked bag and placed that back on the table within seconds.
Ms Barton said she discovered “seven garden pebbles” when she opened the purse the next evening.
Prosecutors said Ms Lakatos then worked with accomplices to make their getaway to France in a rented car.
Two men have already pleaded guilty to conspiracy to steal over the heist.
Ms Lakatos was arrested in France on a European arrest warrant last September and extradited to the United Kingdom.
The trial continues.