An Act to consolidate the Interpretation Act 1889 and certain other enactments relating to the construction and operation of Acts of Parliament and other instruments, with amendments to give effect to recommendations of the Law Commission and the Scottish Law Commission.
The Interpretation Act 1978 applies to itself and to any Act passed after the commencement of the Act (section 22) and, to the extent specified in Part I of Schedule 2, to Acts passed before the commencement of the Act.
Section 5 and Schedule 1 provide definitions of certain words and phrases.
Section 6
Unless it is clear there is a contrary intention, wherever in any Act of Parliament or Statutory Instrument there are words importing the masculine gender, the words should be construed to incorporate the feminine and vice versa. Also, words in the singular include the plural, and as with the interchangeability of words importing gender so it is with the plural and singular.[12]
Where an Act authorises or requires any document to be served by post (whether the expression "serve" or the expression "give" or "send" or any other expression is used) then, unless the contrary intention appears, the service is deemed to be effected by properly addressing, pre-paying and posting a letter containing the document and, unless the contrary is proved, to have been effected at the time at which the letter would be delivered in the ordinary course of post.[14]
Interpretation of the words unless the contrary is proved is discussed in the case of Calladine-Smith v. Saveorder Ltd., as to whether the "contrary" means the contrary of the allegation that the letter was properly addressed, prepaid and posted, or whether it refers to the contrary of the deeming provision that the letter in question was delivered in the ordinary course of post. In this particular case, a letter was shown to have been properly addressed, pre-paid and posted, but not received. On a balance of probabilities the court accepted that the "contrary" to the deemed provision had been proved, the letter was not received, and therefore the deemed provision could not hold.[15]
Section 8
Section 8 specifies that, in general, a measurement of distance refers to measurement in a straight line on a horizontal plane.[16]
R v West London Stipendiary Magistrate, ex parte Simeon [1983] AC 234, HL
Section 18 – Duplicated offences
Section 18 provides:
Where an act or omission constitutes an offence under two or more Acts, or both under an Act and at common law, the offender shall, unless the contrary intention appears, be liable to be prosecuted and punished under either or any of those Acts or at common law, but shall not be liable to be punished more than once for the same offence.[17]
This section replaces section 33 of the Interpretation Act 1889.[18] Humphreys J. said that that section did not add anything to the common law, or detract anything from it.[19]
"... shall not be liable to be punished more than once for the same offence"
The words "same offence" at the end of section 18 do not mean "same act" or "same cause". A person may be punished more than once for the same act.[20] Two prosecutions for a single false statement in a brochure is not oppressive.[21]
See also Williams v Hallam (1943) 112 LJKB 353, (1943) 59 TLR 287, (1943) 41 LGR 165.
A reference to an Act in this section is a reference to an Act to which this section applies.[11]
This section applies to Acts whenever passed.[24] It applies to Measures of the General Synod of the Church of England, and, so far as it relates to Acts passed before 1 January 1979, to measures of the Church Assembly passed after 28 May 1925, as it applies to Acts.[25] It applies to an Act of the Scottish Parliament as it applies to an "Act".[26]
For the application of this section to subordinate legislation, see section 23. And see also section 23A(2)(b).
