The BBC reports:

When officials asked for the Welsh translation of a road sign, they thought the reply was what they needed.

Unfortunately, the e-mail response to Swansea council said in Welsh: "I am not in the office at the moment. Please send any work to be translated".

So that was what went up under the English version which barred lorries from a road near a supermarket.

Thanks to Language Log for the pointer. Earlier this year, Language Log put up an even funnier instance of the same phenomenon.