Lord Donaldson MR’s statement in Corocraft Ltd v Pan-American Airways  2 All ER 1059 at 1071, HL provides a concise exposition of statutory interpretation:
“The duty of the courts is to ascertain and give effect to the will of Parliament as expressed in its enactment. In the performance of this duty the judges do not act as computers into which are fed the statutes and the rules for the construction of statutes and from whom issue forth the mathematically correct answer. The interpretation of statutes is a craft as much as a science and the judges, as craftsmen, select and apply the appropriate tools of their trade. They are not legislators, but finishers, refiners and polishers of legislation which comes to them in a state requiring varying degrees of further processing.”
It defines the clearly distinct roles of Parliament and the courts. Statute may be novel, consolidated or codified in nature, public or private in scope. The English courts role is integral to Parliamentary enactment because legislation in its statutory form is essentially latent requiring courts to implement rules of interpretation to refine, activate and determine a statutes practical application in law.
The rules of construction are principles adopted by the judiciary in addressing three key challenges to cogent interpretation.
These are (1) the inherent uncertainty of language as a communication tool (2) the dichotomy presented by the legislative drafting process and (3) preserving judicial autonomy in observing the declaratory theory of law. The last challenge, the separation of powers and maintaining Parliamentary Sovereignty, is a key theme of Dominic Grieves 2012 speech.
Prior to examining the rules of interpretation, it is important to establish that as Lord Reid highlighted these “are not rules in the ordinary sense of having some binding force” Maunsell v Olins  3 WLR 835 at 837, HL. They are guidelines or conventions adopted by judges and are typically set out in the following sequence: literal, golden, mischief (Rules of Construction) and the purposive approach.
The former Attorney General clearly propagates the literal or plain meaning rule as the essential starting point for interpretation. He qualifies this with a caveat: only the presence of ‘genuine ambiguity and uncertainty’ may necessitate departing from this rule and implementing ‘extraneous material’.
‘Ambiguity and uncertainty’ are in fact a certainty in addressing with the first two challenges. Language is by nature imprecise and ambiguous and the drafting of legislation is dichotomous; “the need for generality can only really be achieved at the expense of clarity and precision of language” (Slapper and Kelly, The English Legal System (2013), p96).
‘Extraneous material’ is here an unqualified generality, however this could encompass (1) the alternative rules of interpretation, (2) the 3 rules of language used to help qualify legislative terminology, (3) the intrinsic aids to interpretation which enable the entire statutory structure to be considered (4) extrinsic aids which after the ruling in Pepper v Hart  AC 593,  1 All ER 42 permitted reference to Hansard and other evidential material and (5) the judicial presumptions protecting against alteration of the common law, the retrospective operation of statutes and preserving court jurisdiction.
The literal rule guides courts to consider specifically the statutory text and not to ascribe their own meaning to that text. The principle here is that “the words selected by Parliament to express its intention in passing the legislation were exactly what it wanted to express.” (Slapper, G, How the Law Works (2007), p.160)
However, as stated, language is by its nature imprecise and equivocal. The instances where application of the literal rule to ambiguously worded legislation, result in an outcome clearly contrary to parliamentary intention and counter to the interests of justice and reason are multiple and well documented. Fisher v Bell  1 QB 394,  3 All ER 731 demonstrates how the limitations of the literal rule necessitate an alternative.
The golden rule is considered an extension of the literal rule. This rule again qualifies that the words and provisions of the statute should be assigned their ordinary meaning, unless this interpretation leads to what Lord Blackburn in The River Wear Commissioners v. Adamson and Others (1876) 1 Q.B.D. 546 described as “an inconsistency, or an absurdity or inconvenience”. The ‘narrow’ application of the golden rule operates to ensure that preference is given to the definition of ambiguous terminology that avoids an ‘absurd’ outcome, as demonstrated in Adler v George  2 QB 7, 1 All ER 628. The ‘wider’ application of the golden rule operates when there is only one clear meaning of a legislative provision, but the literal interpretation of that provision would lead to a legal anomaly contrary to the public interest Sigsworth, Re, Bedford v Bedford  Ch 89,  All ER Rep 113
The mischief rule and the purposive approach can be considered together as they each attempt to ascertain fundamental legislative intent.
The mischief rule directs judicial focus retrospectively to determine the root defect or ‘mischief’ within the common law which the legislation under consideration attempts to remedy, a primary purpose of early legislation being to supplement provisions in the common law. The staged process for identifying and correcting common law defects by statutory interpretation was first established in Heydon’s Case (1584) 3 Co Rep 7a. The rule was applied definitively by the High Court in Corkery v Carpenter  1 KB 102,  2 All ER 745 and more recently in a high profile case before the Supreme Court in R (on the application of the Electoral Commission) v City of Westminster Magistrates’ Court and another  UKSC 40,  1 All ER 1.
More recently, legislation has become the major source of law and its purpose is considerably broader in scope, addressing positively legal, social and technological advances. Courts may be said to be adopting a ‘purposive approach’ when interpreting legislation to fulfil these criteria.
The purposive approach directs judicial focus prospectively. In ascertaining the statutes fundamental purpose, its potential to address challenges not initially envisaged by the legislature can be achieved. The freedom afforded to alter the actual text of restrictions imposed by strict literal interpretation was highlighted by Lord Griffiths in Pepper v Hart  1 All ER 42 at 50, HL
The foundation of the purposive approach lies in European civil law tradition, and the legal principles deduced from the codified body of rules that constitute European law. Consequentially, this approach adopted by English courts can ensure domestic legislation is interpreted and effected consistently with the principles of EU law, and in compatibility with the European Convention rights incorporated into English law by the Human Rights Act (HRA) 1998. This is clearly demonstrated in Pickstone v Freemans plc  AC 66,  2 All ER 803, HL.
Purposive interpretation might appear as an interpretative panacea, however, Lord Scarman in Shah v Barnet London Borough Council  2 AC 309,  1 All ER 226 at 238, HL cautioned that “Judges may not interpret statutes in the light of their own views as to policy“
Therefore a purposive reading of the legislative text must be qualified by the two distinct criteria established by Lord Wilberforce in Royal College of Nursing of the United Kingdom v Department of Health and Social Security  AC 800 at ,  1 All ER 545, HL.
While Lord Denning advocated that “filling in the gaps” in “making sense of the enactment” was an interpretative prerequisite justifying purposive reading of statute in Magor and St Mellons RDC v Newport Corporation  2 All ER 1226 at 1236, this viewpoint was received critically by the House of Lords, Lord Simonds articulating on review of this case ( A.C. 189  2 All ER 839 at 841) that Lord Dennings proposal represented a “usurpation of the judicial function”.
In promoting the literal rule as being an interpretative necessity, Grieve seems to consciously paraphrase Tindal C.J.s’ exposition of this rule in the Sussex Peerage Case (1844) 11 Cl & Fin 85 at 143, HL. However Grieves’ proposition has an inconsistent duality, while theoretically logical it is potentially professionally regressive. It appears to marginalise the alternative rules and aids which have proven essential to interpretation, in particular the ascendancy of purposive reading. This viewpoint alongside concerns his speech highlight about the increasing influence of EU law and the ‘macro-political’ implications of the HRA 1998 appear as partisan rather than legal analysis.
The post of Attorney General, a political appointment should not empower Grieve with the authority to pre-determine judicial protocol. In statutory interpretation, there is no correct rule or correct hierarchical application of rules and aids. This fact is cogently stated by Evans L.J. in R v Fellows; R v Arnold  1 Cr App Rep 244,  2 All ER 548 at 554:
“Whilst the court’s decision in a particular case may indicate what can be described as a ‘purposive’ as distinct from a ‘literal’ approach, it would be wrong in our view to say that one or other of these two methods should be pre-determined or is correct.”
Corkery v Carpenter  1 KB 102,  2 All ER 745, 48 LGR 648
Corocraft Ltd and Another v Pan American Airways Inc  1 QB 616,  1 All ER 82, HL
Duport Steels Ltd and others v Sirs and others  1 All ER 529 at 541, HL,  1 WLR 142
Heydon’s Case (1584) 3 Co Rep 7a
Magor and St Mellons Rural District Council v Newport Corporation  AC 189,  2 All ER 839, 115 JP 613,  2 TLR 935
Pepper (Inspector of Taxes) Respondent v Hart Appellant  A.C. 593,  1 All ER 42 at 50, HL
The River Wear Commissioners v. Adamson and Others (1876) 1 Q.B.D. 546
R (on the application of the Electoral Commission) v City of Westminster Magistrates’ Court and another  UKSC 40,  1 AC 496,  1 All ER 1
R v Fellows; R v Arnold  1 Cr App Rep 244,  Crim LR 524,  2 All ER 548
Shah v Barnet London Borough Council and other appeals  2 AC 309,  1 All ER 226, HL
Sigsworth, Re, Bedford v Bedford  Ch 89, 104 LJ Ch 46,  All ER Rep 113
Smith v Secretary of State for Work and Pensions and another  UKHL 35,  3 All ER 907 at ,  1 WLR 2024
Sussex Peerage Case (1844) 11 Cl & Fin 85 at 143, HL
Manchester, C. and Salter, D. (2011) Manchester and Salter on Exploring the Law: The Dynamics of Precedent and Statutory Interpretation, Sweet and Maxwell, London
Open University (2014) W200 Understanding law Manual 1, Units 1 – 7 (3rd Edition), Oxford University Press, Oxford
Slapper, G. and Kelly, D. (2013) The English Legal System, (14th edition), Routledge, Oxon
Elliot, C. and Quinn, F. (1998) English Legal System (Second Edition), Addison Wesley Longman Ltd, Essex, England
Slapper, G. (2007) How the Law Works, HarperCollins Publishers Ltd, London