Anthony Ward, 50, bought 241,000 tons of cocoa beans and now owns enough to manufacture 5.3 billion quarter-pound chocolate bars.

Mr Ward, who is worth around £36 million, holds so much of the market he could force manufacturers to raise the price of Britain’s favourite chocolate bars.

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Cocoa prices rose by 0.7 per cent as a result of the trade to £2,732 per metric tonne – the highest price for cocoa in Europe since 1977. It follows a series of weak harvests in Ghana and the Ivory Coast, the main areas where the crop is grown.

In 2002 Mr Ward made £40 million in two months after making a similar deal. He bought 204,000 tones of cocoa when West Africa was experiencing poor harvests and political instability in the equatorial area.

He then watched the price of cocoa increase from £1,400 a ton to £1,600 a ton.

Cocoa prices have more than doubled since 2007, following increased demand particularly from China and India, forcing chocolate makers to raise prices and in some cases to change recipes to use less cocoa.

The trade took place on the London International Financial Futures and Options Exchange (Liffe), a market which trades contracts in commodities such as corn, wheat, sugar, coffee and cocoa.

Most of these contracts are “options” or “futures” giving a trader the right to buy these commodities at a certain price at a certain time in the future. What made yesterday’s trade so unusual was that the mystery buyer or buyers took physical delivery of the commodity.

The beans will be stored in one of Liffe’s warehouses in Amsterdam, Antwerp, Bremen, Felixstowe, Hamburg, Humberside, Le Havre, Liverpool, London, Rotterdam, or Teesside.

There have been mounting worries that speculators have been distorting the cocoa market in recent weeks, with brokers writing a letter of protest to Liffe earlier this month.

Barbara Crowther, a spokesman at the Fairtrade Foundation, said that no farmers in West Africa would benefit from the higher prices. She said: “This speculation only serves to increase volatility and uncertainty. Part of the problems in rent years have been the lack of investment in improving cocoa farms. But the farmers have already been paid a set price – none of this money will filter down to them.”