While the global recession has hit most commodities hard, the red metal has defied gravity and last week hit highs for 2009. Copper contracts for delivery in three months' time closed at $5,522 on Friday, 76pc ahead of the low on Christmas Eve last year.

One trader said: "It looks funny. There are vast volumes being bought in the markets, it's got all the hallmarks of someone trying to corner the market."

Ever since 1996, when Yasuo "Mr Copper" Hamanaka of Sumitomo Bank managed to buy 5pc of the copper market in what was then the world's biggest fraud, the non-ferrous metals market is periodically swept up in conspiracy theories of foul play and manipulation.

Subsequent "Mr Copper" scares have ranged from the spurious to politically controversial. The sharp rise in copper futures this year is good enough reason for the latest bout of rumours. Once again China is a prime suspect where there has been strong buying interest. But there are other theories too.

Some traders argue that some of the biggest firms could be trying to corner the market to keep their share prices high in what has been a torrid time for commodities firms.

All the big firms deny this as nonsense while the LME itself has told several individuals who have complained that it can see no irregularities.

Right or wrong, the conspiracy theories can abound because copper is both illiquid and cannot easily be transferred around the world to meet shortages. Capturing a small percentage of the market can allow a stockpiler to control the price of the metal.

For instance, although many speculators knew Mr Hamanaka was manipulating the market, if anyone attempted to short copper the trader would use Sumitomo's might to pour more cash into his positions, thereby sustaining the price and outlasting the shorts, simply by having deeper pockets.

In doing so, however, he accumulated losses of $1.8bn (£1.1bn). When the fraud was discovered, the copper price plunged. Sumitomo's total losses were reckoned at $2.6bn.

In 2005, copper markets were again hit by the "the mystery of the phantom copper dealer" in China. At the time, the benchmark three-month future contract jumped to a new all-time high in excess of $4,100 after Liu Qibing, a Chinese copper trader, disappeared. He built up a short position of between 100,000 - 200,000 tonnes of the metal on behalf of the State Reserve Bureau (SRB), the organisation that manages China's strategic metals reserves.

This time experts insist it is different – and there is no mystery to the price of copper. For a start, copper prices have jumped 76pc this year but remain almost 40pc below the record $8,930 a tonne reached in July 2008.

Analysts at Goldman Sachs expect the price to be "substantially above the market forward curve" and reach $5,800 per tonne by the end of 2010. A recent note from the investment bank said: "Recent data releases out of Brazil, China, India, and Singapore have all surprised on the upside. Even in the more mature economies, automobile production is likely to rebound later this quarter."

Copper is used in wiring cars, with electric vehicles needing twice as much wiring as a petrol vehicle.

In a note this month, Morgan Stanley said that copper is the bank's "favoured base metal exposure".

The research noted that, despite a "significant fall in consumption in the developed world in [the first half of 2009], emerging market consumption has remained resilient, especially in China". Whether this is China restocking while prices are low or an actual reflection of consumption is the subject of much debate. There is also the view that China is buying copper as an investment as a way of diversifying away from its substantial dollar holdings.

Morgan Stanley adds that there are longer-term factors that are pushing up the price of copper too. It notes growing signs of structural shortages in the copper scrap market, and also a long-term grade decline among some of the world's largest and historically most productive mines. "Both of these supply-side features of the market are likely to become more pronounced," the note said.

But some LME traders are unconvinced: "This isn't anything to do with market forces, it's manipulation. You'll see."