Sir Beves of Hampton is one of a handful of Middle English romances in which unexpected and not always obviously motivated changes in verse form occur at some point in the text. The Auchinleck text of Guy of Warwick offers the best-known and least problematic example of the phenomenon. There the shift from couplets to tail-rhyme stanzas appears to mark a deliberate narrative caesura: a new section of the poem begins and the sense of a fresh start is underscored by the insertion of exordial material unparalleled in the Anglo-Norman original of the poem and its other Middle English redactions. The two tail-rhyme stanzas that introduce the Auchinleck version of Richard Coer de Lion remain a puzzle, while the change from septenary couplets to tail-rhyme stanzas halfway through the Ashmole Sir Ferumbras has been convincingly attributed to a change in the source text used by the Ashmole author/ translator.1 In all these narratives the sudden shift is limited to a single manuscript: the only manuscript of this redaction of Ferumbras, but one of several in the cases of both Guy and Richard. Beves is unique in that five of its six manuscripts, representing four different redactions of the poem, switch from couplets to tail-rhyme stanzas more or less simultaneously.2 Such uniformity has made it harder to account for the change by reference to scribal whimsy, and there has been some debate over the years about what might have prompted it. In what follows I shall suggest that this odd feature of the versification of Beves is a direct consequence of the constraints under which the translator of the Anglo-Norman Boeve de Haumtone had to work.3A translator's work is subject to a complex web of hierarchically ordered constraints. The most important, and the one over which the translator has the least control, is obviously language. Versification is less constraining in that prosodie form, unlike language, can be chosen with a certain degree of freedom; once chosen, however, it too exerts a powerful restrictive influence on a translator's choices at all textual levels. The Middle English translator of Boeve exercised his freedom of choice in a way that has puzzled the critics of the text. Unlike later translators, he did not have to worry about whether to use verse or prose for his rendering of the Anglo-Norman narrative. At this early date prose was not a real option, as the great flowering of prose romances in thirteenth-century France had no parallel in England.4 Verse was the norm, and the main question was, what kind of verse? The answer, it seems, was not obvious. A salient feature of the versification of Beves is the abrupt change from six-line tail-rhyme stanzas to rhymed couplets at line 47 5 in manuscripts A, E, and C. (In SN the tail-rhyme pattern continues until line 528.) Eugen Kolbing, the romance's first editor, rejected the possibility that the couplet section of the poem was 'the work of a continuer [sic], who found the stanza too difficult or not according to his taste'. As there was nothing 'to correspond with this change in the original French versions', Kolbing felt compelled to accept the shift in verse form as yet another example of what is, after all, not an isolated phenomenon in Middle English literature.5 Derek Pearsall, who made no secret of his low opinion of Beves's, artistic value, conjectured that 'a different hack' might have taken over or that 'the English adaptor recognized the unsuitability of the more poetic measure to this vulgar thriller'.6 Dieter Mehl suggested 'that the first part of the poem was also originally written in rhyming couplets which by slight alteration, in many cases merely by the insertion of caudae, were turned into tail-rhyme stanzas'.7 This is very likely true of the continuation of the stanzaic pattern in SN (lines 475 - 528), which a comparison with AEC shows to be by and large the result of the mechanical addition of tail lines to existing couplets. For the earlier section of the narrative, however, this is not the case. …