On enquiring about inquiry

A correspondent reports something he was reading in The Times this week:

1356 BST: Jemima Khan has a complaint about the police investigation into phone hacking. 'Not much hope for hacking Inquiry when they can't even spell it... I received "Operation Weeting Enquiry [sic] Questionnaire" last week,' she tweets.

He notices that I often write in my blog about enquiries from correspondents. He concludes: 'What are the rules and/or usage in British English? I know that in American English it is always inquiry.'

Well, not always, actually. The Cambridge Corpus of American English shows a preference of 97% for inquire and 88% for inquiry. That's a dominant usage, certainly, but not a universal one. In Britain, the picture is extremely mixed. The British National Corpus shows almost exactly twice as many enquire as inquire, and twice as many inquiry as enquiry. The world picture, amalgamating different spelling traditions, is mixed too. Google shows inquire five times more common than enquire, and enquiry seven times more common than inquiry. But all four forms are frequent. Not surprisingly, then, most dictionaries throw in the towel and say the i- and e- forms are interchangeable. The OED, for example, simply lists them as alternatives, but adds a note under enquire:

'An alternative form of inquire v. The mod. Dicts. give inquire as the standard form, but enquire is still very frequently used, esp. in the sense "to ask a question".'

Could there be a sense difference? Prescriptive grammarians tried to find one, citing the difference between insure and ensure as justification, and their view did have some influence. The i- forms should refer to impersonal, formal investigations, it was recommended, whereas the e- forms should be used only for personal questions, and doubtless many people tried to make their usage conform to this distinction. The lists of examples in the large corpora, however, show many counter-examples, and it is difficult to resist the conclusion that, for most people, the forms are as interchangeable as judgment and judgement - in other words, influenced by such factors as region, house style, and institutional preference, but not by anything semantic.

The original forms in English were with e- (from French enquerre), but in the late 14th century we see i- spellings appearing, as people tried to reflect the Latin origin of the words (inquirere) - a common practice at the time. Dr Johnson put all his weight behind the i- forms in his dictionary, and doesn't include the e- forms at all. Modern style guides seem to be going the same way. The Cambridge Guide to English Usage (2004), for example, concludes thus:

'Given no consistent ways of differentiating the two spellings, and the fact that differentiation is unnecessary, it makes sense to consolidate the use of one or the other. Inquire and inquiry recommend themselves as the spellings made first among equals by the Oxford Dictionary, and the fact that they are strongly preferred in North America.'

That doesn't make the e- forms wrong, of course, as the quotation from my correspondent suggested. And it's nonsense to suggest there might be a correlation between this choice of spelling and the conduct of a policy enquiry.