In massive volumes of 2.7 billion pounds in morning trade alone, copper for delivery in December slumped to a low of 2.9710 a pound ($6,550 per tonne), down more than 2% from Tuesday's close to a three-week low.

A week ago copper hit an intra-day high just shy of $3.18 a pound (more than $7,000 a tonne), the highest since September 2014. But disappointment about imports by China, responsible for some 46% of global consumption of the metal, rising stock levels at LME warehouses and receding mine supply worries saw the rally come to a screeching halt.

The prospect of a weakening renminbi also emerged as a factor behind the pullback after Chinese policymakers this week relaxed rules to curb speculation against the yuan which had been in place for nearly two years.

A correction on copper markets may also have been overdue as speculative interest has been running ahead of industry fundamentals. Hedge funds built successive record net long positions – bets on rising prices – in recent weeks which according to the latest report totalled the equivalent of more than $9 billion at today's prices.

Reports at the end of July that China is planning to ban the importation of scrap copper by the end of next year sparked the rally from copper's summer lows, but caught many in the industry by surprise.

Investment banks and institutions are now catching up and according to the September survey by FocusEconomics released yesterday, eight of the 24 analysts polled upgraded their fourth quarter forecasts compared to projections made the month before.

However, while no-one downgraded the outlook for copper consensus forecasts remain well below ruling prices.

Analysts project that prices will average $5,870 per tonne in Q4 2017 and $5,844 per tonne in Q4 2018. The lowest forecast for Q4 2017 is $4,899 per tonne, while the maximum forecast is $6,674 per tonne. Barclays, Deutsche Bank, JP Morgan and Macquarie all see prices averaging more than 15% below today's price going into 2018.

The price forecasts for Q4 2017 were raised for nine metals and minerals, including aluminium, lead and iron ore. Tin was the only exception with economics lowering their price expectations for the rest of the year.