_Procedure._--Formerly letters patent were always granted under the Great Seal. But now, under the Crown Office Act 1877, and the Orders in Council made under it, many letters patent are sealed with the wafer great seal. Letters patent for inventions are issued under the seal of the Patent Office. The procedure by which letters patent are obtained is as follows: A warrant for the issue of letters patent is drawn up; and is signed by the lord chancellor; this is submitted to the law officers of the crown, who countersign it; finally, the warrant thus signed and countersigned is submitted to His Majesty, who affixes his signature. The warrant is then sent to the Crown Office and is filed, after it has been acted upon by the issue of letters patent under the great or under the wafer seal as the case may be. The letters patent are then delivered into the custody of those in whose favour they are granted.
_Construction._--The construction of letters patent differs from that of other grants in certain particulars: (i.) Letters patent, contrary to the ordinary rule, are construed in a sense favourable to the grantor (viz. the crown) rather than to the grantee; although this rule is said not to apply so strictly where the grant is made for consideration, or where it purports to be made _ex certâ scientiâ et mero motu_. (ii.) When it appears from the face of the grant that the sovereign has been mistaken or deceived, either in matter of fact or in matter of law, as, e.g. by false suggestion on the part of the patentee, or by misrecital of former grants, or if the grant is contrary to law or uncertain, the letters patent are absolutely void, and may still, it would seem, be cancelled (except as regards letters patent for inventions, which are revoked by a special procedure, regulated by § 26 of the Patents Act 1883), by the procedure known as scire facias, an action brought against the patentee in the name of the crown with the fiat of the attorney-general.
As to letters patent generally, see Bacon's _Abridgment_ ("Prerogative," F.); Chitty's _Prerogative_; Hindmarsh on _Patents_ (1846); Anson, _Law and Custom of the Const._ ii. (3rd ed., Oxford and London, 1907-1908). (A. W. R.)