On being orient(at)ed

A correspondent writes to ask if it should be disoriented or disorientated.

The answer partly depends on where you live. If you're American, you're in no doubt that it must be the shorter form; and according to Pam Peters (in her Cambridge Guide to English Usage) the same preference is found in Canada and Australia. Some US style guides go so far as to say that orientate is simply incorrect. That's going too far, as British English uses both, with a noticeable preference for the longer form. H...