A Guardian journalist who was researching prices at a Tesco supermarket was threatened with arrest for writing down prices as he walked around. The security guard who questioned him claimed that it was illegal to write down prices at Tesco's. The manager later allowed as how it wasn't illegal, merely against store policy.

Of course, Tesco can set any policy it wants for its premises (provided those policies don't violate other laws, such as laws regarding discriminating on the basis of disability, race or sex). But Tesco's customers can also ask pointed questions about those policies, such as, "If Tesco's prices are so great, why are they afraid of having people know what they are?" In this case, Tesco's had priced its bulk water so that it was more expensive than individual bottles — just the sort of thing you might want a pad and paper handy to work out before you gave them your money.

And, of course, it's legal to do anything inside a Tesco that would be legal on the street outside, and Tesco's only remedy for violations of its policies is to ask you to leave.

"It's illegal to write things down and you can't take any photographs, either. If you want to check the prices, take the item to the till and pay for it there. The price will be on the receipt," he said, pointing me to the exit… If we on Guardian Money bought every item available in Tesco, Sainsbury's, Morrisons or Asda every day, we would be able to check prices, and see if that bottle of wine, or those washing powder tablets, really are half price. But we can't, and trading standards officers don't have the resources to, either. Spot checks are about the best we can do. But even that, it appears, is unacceptable to the likes of Tesco. Next time I'll wander round the store speaking the prices into my mobile phone. It's got a record function. Note to Tesco company policy writer: ban customers from speaking into their phones.

Now it's illegal to write down prices in a Tesco supermarket

(Thanks, @sicckid1972!)

(Image: Tesco, a Creative Commons Attribution Share-Alike (2.0) image from loopzilla's photostream)