I've solved my own question. The reason I'd not found it immediately was that I'd got it in my head that it was "the clear light of the day", and was an English song. In fact it was "the clear air.” The song being the Irish song, "The Lark in the Clear Air.”

Here is Kate Winslett singing it from the film, and not at all bad either

And here are the words and a midi of the tune

HTML link fixed. --JoeClone, 30-Jan-02.