Occasionally, mistakes are made in granting Royal Assent to Bills. It appears that the practice has been to rectify these mistakes by means of further legislation. The following is from Frederick Clifford's A History of Private Bill Legislation (1885):
"In 1830, a public Bill to amend the law relating to the employment of Children in Cotton Factories received the Royal assent by commission and thereby became an Act before it had gone through all its stages, an amendment made by the Lords not having been communicated to the Commons. A Committee was appointed by the Lords to inquire into the mistake, and at a conference the Commons requested an explanation. At another conference this explanation was communicated, and being deemed satisfactory by the Commons, they introduced a Bill to render the previous Act valid. This Bill was accordingly passed with the utmost despatch, Standing Orders being dispensed with; and it received the Royal assent in the usual course.
It became necessary to pass an Act to rectify a mistake which had occurred in 1844 in giving the Royal assent, by commission, to two Eastern Counties Railway Bills. One of these was called the Eastern Counties Railway Bill; the other, the Eastern Counties Railway (Brandon and Peterborough Extension) Bill. The latter of these Bills, which had not gone through all its stages in the House of Lords, was inserted in the commission and, accordingly, on May 10th received the Royal assent instead of its sister Bill, which had passed both Houses. The amending Act provided that when the Eastern Counties Railway Bill received the Royal assent, it should be as valid and effectual to all intents and purposes from May 10, 1844, as if the title thereof had been properly inserted in the commission, and it had received the Royal assent on that day; and that the Brandon Bill and all proceedings thereupon should be "in the same state as if the title thereof had not been inserted in the commission," and should not be deemed to have received the Royal assent."
