A massive seam of money has been discovered in County Durham.

The deposit was found by building workers who were excavating the foundations for a new factory. The site near Durham City is owned by the Japanese pet food company, Tiggerchunks.

An eyewitness reports: "The lads were drilling through some rock and suddenly there was money everywhere, we didn't know what was going on. We collected as much as we could and reported it to the boss." Most of the workers have not been seen since, despite the "generous" offer of a £200 bonus.

There are estimated to be many billions of pounds worth of crisp £20 notes, which the company's radiometric dating techniques show were laid down in the Carboniferous period. Amazingly, the Bank of England has confirmed the notes are legal tender in the UK.

A huge security operation has been mounted to protect the find. A private security firm is using guard dogs and, more controversially, armed guards and ant-personnel mines. In contrast the extraction process couldn't be simpler. "A simple money-grab will suffice", said a spokesperson for Tiggerchunks. "We just lift the money and take it to the bank."

The Treasury has commented that the release of such a large amount of money into the UK economy could have a significant inflationary impact. "The company will only be granted a permit to extract limited quantities for scientific purposes." It is thought this could be worth up to £300 million a year.