Traders and clerks work at the London Metal Exchange in London, Britain on June 18, 2019.

Traders and clerks work at the London Metal Exchange in London, Britain on June 18, 2019.

Traders and clerks work at the London Metal Exchange in London, Britain on June 18, 2019.

Traders and clerks work at the London Metal Exchange in London, Britain on June 18, 2019.

Traders and clerks work at the London Metal Exchange in London, Britain on June 18, 2019.

Traders and clerks work at the London Metal Exchange in London, Britain on June 18, 2019.

Traders and clerks work at the London Metal Exchange in London, Britain on June 18, 2019. The London Metal Exchange (LME) is one of the world's largest markets in options and futures contracts on base and other metals. (Photos: Xinhua/Han Yan)

Open-outcry is the oldest way of trading on the exchange, though nowadays the majority of trades are placed electronically. The LME is the last exchange in Europe where open-outcry trading takes place. (Xinhua/Han Yan)

Traders and clerks work at the London Metal Exchange in London, Britain on June 18, 2019.

Traders and clerks work at the London Metal Exchange in London, Britain on June 18, 2019.

Traders and clerks work at the London Metal Exchange in London, Britain on June 18, 2019.

Traders and clerks work at the London Metal Exchange in London, Britain on June 18, 2019.