Peniarth MS 28 (formerly Hengwrt MS 7), containing a Latin copy of the Laws of Hywel Dda, belongs to one of the National Library of Wales's foundation collections of manuscripts, the Peniarth Manuscripts, most of which come from the library of the seventeenth-century Welsh antiquary, Robert Vaughan of Hengwrt (1592?-1667). The manuscript comprises twenty-five vellum folios and measures 190 x 145 mm. (written space c. 145 x c. 115 mm.). It was rebound in red leather at the National Library in 1940.
The 'Laws of Hywel Dda' is the term applied to a system of native Welsh law named after Hywel Dda (died 950) who is credited with its codification. None of the surviving Welsh law manuscripts, however, is earlier than the second quarter of the thirteenth century. Although they contain law that is of twelfth- and thirteenth-century origin, scholars are agreed that these manuscripts contain a core of matter that is much earlier in date. Most of these books are small in size and were probably designed as 'pocket-books' to be carried about by lawyers rather than to be kept on library shelves. Peniarth MS 28 belongs to this first generation of law-books, being written probably in the middle of the thirteenth century, a date arrived at by Daniel Huws on palaeographical and physical grounds; this challenges J. Gwenogvryn Evans's dating of the last quarter of the twelfth century. However, the manuscript differs from its contemporaries in a number of respects. It is much larger than the other law-books of the period, probably intended for a library rather than the pocket of a lawyer, and it is written in Latin rather than in Welsh. But what singles it out most is the series of illustrations it contains portraying the king and the officials of his household. The conclusion to be drawn is that the scribe of Peniarth MS 28 had been commissioned to write a special copy of the Welsh laws, probably a presentation copy for some dignitary. The fact that it is written in Latin suggests an ecclesiastic rather than a lawyer, maybe a non-Welshman. Textual evidence suggests that it was probably written in south-west Wales.
It is known that, by the beginning of the fourteenth century, the manuscript was at St Augustine's Abbey, Canterbury. The evidence for this comes from one of two pastedowns preserved at the end of the volume. These are all that remain of the original 'old oak boards binding' seen by J. Gwenogvryn Evans at the end of the nineteenth century, when it was still at Peniarth, Merionethshire. One of these bears the press-mark of the library of St Augustine's Abbey, Canterbury, and the name of the donor, now partly illegible but interpretable as that of William Byholte (fl. 1292-1318), prior of the abbey. It is also thought that this was the copy of the Welsh laws consulted by John Peckham, archbishop of Canterbury, 1279-94, when he sent his letter to Prince Llywelyn ap Gruffudd in 1282, denouncing the prince's morals and those of the Welsh, and in which he makes two references to the Laws of Hywel Dda. The manuscript was still at Canterbury at the end of the fifteenth century, as 'Leges Howelda Wallici' appears in the catalogue of the abbey's library compiled c. 1491-7 (Dublin, Trinity College Library MS 360). Its subsequent history, however, until its acquisition by Robert Vaughan of Hengwrt, is not known. The library catalogue once belonged to the astrologer Dr John Dee (1527-1608) and alongside the above entry, Dee has written 'Leges Howelis Da'. It is known that Dee acquired many manuscripts from St Augustine's, Canterbury, but there is no direct evidence that Peniarth 28 was one of them.
The illustrations contained in the volume must be regarded as a rarity for medieval Welsh manuscripts. They fall into two categories, firstly those which portray the king and some of the officials of his household, together with some other human figures, and secondly those which depict birds, animals and items of legal value. The representation of the king seems to be based upon a higher-quality archetype than the rest of the drawings, which are crude and lack sophistication. They are probably the work of the scribe as they appear to have been drawn in the same kind of ink as the text. Apart from the ink, he uses two main colours, green and red. Assuming a mid-thirteenth century date for the manuscript, the scribe's use of green rather than the more common blue used at that date, especially for the capital letters, must be regarded as an archaism.