The man accused by Trafigura Group of being behind a $590-million nickel fraud finally responded to the allegations, claiming that Trafigura itself “devised and proposed” the scheme.

In a defense filed to a London court on Wednesday afternoon, lawyers for Prateek Gupta said Trafigura employees had proposed an arrangement whereby the two sides would agree contracts for nickel but in fact trade other material.

The claim is the latest twist in a case that shocked the metals industry, when Trafigura in February revealed it had lost more than half a billion dollars buying cargoes of nickel from Gupta’s companies only to discover that they contained much lower value materials.

Gupta said in the filing that Trafigura had approached him in 2019 seeking to significantly increase its nickel trading with his companies.

According to Gupta’s account, during a meeting in June 2019 at a hotel on Dubai’s Palm Jumeirah, he discussed trading metals that “bore some resemblance to nickel” as if they were actually nickel with Socrates Economou, Trafigura’s then head of nickel, and Harshdeep Bhatia, a senior Trafigura trader based in Mumbai.

The two Trafigura traders “stressed to Mr. Gupta that the actual purity, specification, and value of the materials in fact being traded was unimportant to Trafigura,” Gupta claims.

It’s unclear what evidence Gupta has to support the claim beyond his own recollection of the meeting. Trafigura in February secured a freezing order against Gupta. In its court filings at the time, the trading house raised the possibility that Gupta might claim it was aware that nickel was not being shipped, but said that it would dispute such an argument.

Both Economou and Bhatia have left Trafigura in the wake of the alleged fraud, Bloomberg has reported. Trafigura has consistently said it doesn’t believe that any of its employees was complicit.

A Trafigura spokesperson had no immediate comment. Economou declined to comment and Bhatia didn’t immediately respond to requests for comment.