The Charter deals only with tenure by knight’s service; nothing is said of other tenures. The explanation of the omission may possibly be different in the cases of socage and of serjeanty respectively.[361] (_a_) _Socage._ The barons were not so vitally interested in socage, that being, in the normal case, the tenure of humbler men.[362] In later reigns the king, like an ordinary mesne lord, contented himself with one year’s rent of socage lands in name of relief. (_b_) _Serjeanty._ The barons cannot have been indifferent to the fate of serjeanties, since many of them held great estates by such tenures. Possibly they assumed that the rules applied to knights’ fees and baronies would apply to serjeanties as well. The Crown, however, acted on a different view; large sums were frequently extorted by Henry III. By the reign of Edward I., however, the practice of the exchequer was to limit itself to one year’s rent (a sufficiently severe exaction)[363] for serjeanties, which thus fell into line with socage.[364] ----- Footnote 361: Cf. _supra_, pp. 66-9. Footnote 362: It is possible to argue that the custom as to socage was already too well settled to require any confirmation. Glanvill (IX. c. 4) stated the relief for socage at one year’s annual value. It is not absolutely clear, however, whether this restriction applied to the crown. Further, no custom, however well established, was sufficiently safe against John’s greed, to make confirmation unnecessary. Footnote 363: See Littleton, _Tenures_, II. viii., s. 154, and Madox, I. 321, who cites the case of a certain Henry, son of William le Moigne, who was fined in £18 for the relief of lands worth £18 a year held "by the serjeanty of the King’s Lardinary." Footnote 364: Cf. _supra_, p. 69. ----- II. _Units of Assessment._ Some explanation is required of the three groups into which crown estates were thus divided—knight’s fees, barons’ baronies, and earls’ baronies.