Never published, Herbert Butterfield’s 1965 Gifford Lectures at the University of Glasgow are available (in draft form) from the University of Cambridge (Manuscripts/MS Butterfield 140). The library’s website gives the following detail:

1) Gifford Lectures: ‘The Beginnings of historical writing’, ‘Kings and priests - the historiography of the pre-Classical empires’ and ‘The originality of the Old Testament’. Drafts, some in Butterfield’s hand and some typescript.
2) Notes and drafts in Butterfield’s hand concerning historiography, some taken from printed sources, and referring in particular to ancient history. Apparently made in relation to the Gifford Lectures.