to be most valuable to us. Of course, any system of law may contri- bute something to our understanding of Welsh law, just because it is law and governs human relations: so Maine and T. P. Ellis made use of what they had learnt in India; but when we have to pick and choose our starting-point, we should be well advised to start nearer home. The law of the Punjab is not a good starting-point because it is too remote; nor is Roman law or post-medieval English law, because it is too sophisticated; we can expect results most quickly if we concentrate first on the medieval systems of western Europe. Among those systems Irish law has an obvious primacy, and I hope I shall not be misunderstood if I urge a certain caution in using Irish law, for I am particularly conscious of my own debt to those who have worked on Irish law. But there seem to me to be two reasons for caution--one permanent, the other temporary. The permanent reason for caution is also the reason for the great value to us of Irish law: the fact that Irish law is preserved in a form so much earlier than that of Welsh law. The Irish manuscripts give us early law texts glossed and commented on, rather than law developed and amended, such as we find in the Welsh manuscripts. This means that compari- sons with Irish law are invaluable when we are seeking the original form of the Welsh rules: so the explanation of the development of mach, given above, rests largely on a basis of work on the correspond- ing Irish institutions.24 But (as we saw with mach) a legal institution may change its significance without changing its name; hence an Irish comparison must be very carefully handled when we come to examine the meaning of a Welsh institution in the twelfth or thirteenth century. The temporary reason for caution is of even greater practical importance. This reason is that the Irish material is particularly difficult to use both because its language is so archaic and because so much of it has as yet not been adequately edited. To deal with the unedited and inadequately edited Irish material, a much higher degree of competence in a much more difficult language is needed than for any of the Welsh material; so the legal historian who is not a quite exceptional Celtic scholar will be well advised to confine himself to the properly edited material. Fortunately the study of Irish law is being vigorously carried on in Ireland, and we in Wales can benefit from this work, the more so because Irish scholars make such good use of the more tractable Welsh material in comparisons. 24 See D. A. Binchy, Early Irish Society, ed. Myles Dillon (Dublin. 1954). pp. 63-4.