Look inside on the actual footbed of the shoe and you should see some numbers stamped there. I think they only ever stamp the UK size of the shoe there, irrespective of who the shoes were made for. If there's a difference between the stamped number and the printed number then the printed number is most likely the US size.
Wow, I wish I knew this a few days ago! I would have liked to have seen what was actually stamped inside the Barneys "Two Eye Chukka" before I sent them back, a UK 9 or 9.5 for a US 10D.