A lone trader seeking bragging rights and a minute of fame was behind the record rise in oil prices to $100 prices a barrel, according to market watchers.

They claim the single trader bid up the price by buying a modest lot and then sold it immediately at a loss.

Meanwhile, the New York Mercantile Exchange said that US crude oil futures traded just once in triple figures on Wednesday.

Some analysts questioned the validity of the trade, though their concerns faded as oil set a record yesterday, with New York light sweet crude climbed to a new high of $100.05 a barrel.

On Wednesday, one floor trader bought 1,000 barrels, the smallest amount permitted, and sold it immediately for $99.40 at a $600 loss, said Stephen Schork, a former floor trader on the New York Mercantile Exchange and the editor of an oil market newsletter.

"They absolutely overpaid," he told Radio Four's Today Programme.

"He paid $600 for the right to tell his grandchildren that he was the first in the world to buy $100 oil."