Amidst far-reaching and obvious constitutional change of the scale of leaving the EU, it is easy to lose sight of other less prominent and subtler changes. One such change is the proliferation of codes, concordats and texts that furnish official accounts of many of the UK's most important constitutional rules and principles. Examples include the Cabinet Manual, the Ministerial Code and the Civil Service Code. In The Codes of the Constitution, Andrew Blick examines this process of “codification”. In public law, this term is more commonly used to denote the process whereby a customary “unwritten” Constitution is transformed into an entrenched “written” Constitution. However, Blick uses the term in a broader sense to denote the formalisation of constitutional rules and principles into official, publicly promulgated and typically (but not always) non-legal texts. Like so much constitutional change, the gradual codification of what Peter Hennessy termed “the hidden wiring” of the UK Constitution has tended to occur haphazardly, through discrete projects, yet it has also unleashed wider change of its own. The very act of preparing so many codes creates the impression that codification is itself part of good governance. The causes and consequences of the progressive codification of the UK Constitution have not received sustained scholarly attention. This book is a welcome exception.

Blick's starting point is that codification is “a literature project of breathtaking scale, scope and complexity”. His aim is not merely to study the content of constitutional codes, but also the political contexts in which codification occurs; “as well as looking at codes”, Blick seeks “to look behind them”. Part One examines the phenomenon of codification (its origins, growth and impact), while Part Two discusses the content of various codes. Throughout the book Blick has a selective focus, concentrating for the most part on UK-wide codes, with an emphasis on codes relating to the executive, rather than codes made by the devolved institutions. Selectivity helps to ensure that Blick's task is manageable. It also builds on his previous research into the civil service and the office of prime minister. But it does so at the cost of potentially revealing comparisons of how codes are drafted and deployed across the UK's territorial Constitution. Amongst Blick's dominant interests are the motivations of the actors responsible for preparing codes. Blick maps close connections between the codes and the culture, priorities and needs of the civil servants who were responsible for drafting them. Another of Blick's chief concerns is how codes can subsequently shape the political environments from which they emerge. One of the book's central themes is that codes not only reflect how actors perceive relevant rules and principles in a specific political environment, but can also help to re-fashion perceptions of that environment.

In chapter 1 Blick offers a review of the historical origins of codification. It makes for rich and rewarding reading. He traces codification to the culture of note taking that is so deeply ingrained within the civil service, pointing to significant milestones such as the creation of the Cabinet Office in 1916. The Cabinet Office has been the primary driver of codification. One of the Cabinet Office's main functions was to minute cabinet meetings and, more generally, to ensure the production and circulation of papers across Whitehall in order to secure more systemised government. Especially interesting is the history that Blick recounts of the Question of Procedures for Ministers (‘QPM’), the precursor of the Ministerial Code. He relates the QPM's early years to the character and workplace traits of the post-World War II Prime Ministers. The QPM was first issued by Clement Atlee, who stressed efficiency and routine in government. Its content was scaled back during the second premiership of Winston Churchill, reflecting his preference for informal modes of governmental business. But, as Blick explains, what was important was that the QPM survived the transition from a Labour to Conservative prime minister. Since the 1940s central government has developed a habit of articulating in official texts its understanding of governmental practices. Blick notes that most of these codes (such as the QPM) were originally intended to remain unpublished, with their availability restricted inside Whitehall, let alone outside. The key purpose of preparing codes was to ensure consistency and continuity of constitutional practice inside government, not to foster public understanding of the workings of government. It is only over the last 25 or so years that previously confidential codes have become publicly available.

Codification since 1979 is the focus of chapter 2. Blick identifies a number of factors that have propelled codification over the last 40 years, including: the greater emphasis on transparency; growing concerns about probity in public life, especially during the 1990s; the need to map more clearly rules and principles in the territorial Constitution; and the increasingly prominent roles played by select committees, who typically have initially pressed for information about various constitutional codes before carving out a role for themselves in scrutinising their operation. Codes normally perform multiple purposes. Amongst the most common are: to systematise practice; to regulate external relations; and to regulate interaction between institutions during a period of declining trust. Blick explains how constitutional codes often take on particular prominence as a tool for regulating institutional relationships where trust and mutual respect is waning. Codes have a mixed record as tools for managing conflict: they do not necessarily end conflict and can themselves become disputed. A central theme to emerge from chapter 2 is that not only has the number of constitutional codes increased over 40 years, but the content of codes has expanded as well, with greater detail now included within. More institutions are also now preparing codes, and more of the codes are being published.

The growing reliance on constitutional codes is a phenomenon found in a number of common law systems, as Blick observes in chapter 3. There is a substantial overlap in the issues addressed in codes in countries such as Australia, Canada, New Zealand and the UK, although as Blick explains this can be explained in part by the fact that drafters in the various countries have drawn significantly on each others’ texts. The discussion of codification in Australia and Canada shows how codes are increasingly used in countries with “written constitutions” as well as in countries with “unwritten constitutions”. This is a useful guard against any lazy assumption that codification as examined in the book only occurs in customary constitutions that have eschewed entrenched and sacrosanct texts with a higher legal status. In considering codification in comparative perspective, Blick dances lightly – and almost cursorily at times – over developments in Australia and Canada. He devotes much more attention to New Zealand, where special importance has been attached to the Cabinet Manual as an authoritative guide to central government decision-making and, more generally, New Zealand's constitutional arrangements as understood from the vantage point of the executive. Chapter 3's comparative analysis is a useful addition to the book, although it is disappointing that this did not extend to comparing how constitutional codes have been used in different parts of the UK.

Blick reflects on the impact of codification in chapter 4, pointing in particular to how codes can shape how constitutional rules are perceived, how rules change and broad conceptions of the legitimacy of those rules. The chapter discusses in some depth the relationship between constitutional codes and constitutional conventions. This is one of the most interesting sections of the book, complementing as it does Blick's earlier writing on conventions. Blick describes a complex relationship between conventions and codification. Codes can buttress conventional rules, for example by raising awareness of conventions and increasing the costs of not complying with them. But codes can undermine conventions, for example by restricting the scope for conventional rules to evolve (although, as Blick notes, some of the evidence – relating to the Cabinet Manual in New Zealand, for example – disputes the claim that codification risks freezing the development of conventional rules). By expressing certain conventions but not others, codes can indirectly undermine the importance of those conventional rules not included with them. More generally, as Blick notes, codification is not a means of achieving secure control over conventions; rather codes are a tool for influencing the broad landscape within which conventions emerge and operate.

Part Two of the book discusses the content of various codes. The coverage is wide: Blick devotes chapters to the influence of codification on the office of prime minister (chapter 5), the Cabinet (chapter 6), other ministers, departments and the civil service (chapter 7) and Parliament (chapter 8). There are also chapters on the codes relating to general elections and the formation of governments (chapter 9), local and devolved government (chapter 10) and, finally, the judiciary (chapter 10). These chapters cover considerable ground, with the discussion of the Cabinet Manual a particular highlight. In these chapters Blick draws several more general lessons. Codification is used, for example, to render explicit just how little we know about how cabinet government operates in practice. Similarly, Blick notes how the publication of the Cabinet Manual shows just how opaque many aspects of the office of prime minister have been. Although full of useful detail, Part Two of the book prioritises description over analysis (or at least the analysis in these chapters is often shoehorned into a few pages). It also lacks the richness and colour found in Part One.

The chapter on the judiciary and the rule of law will be a special disappointment to many lawyers. In this chapter Blick falls far short of his stated aim of not only looking “at” the codes, but of also looking “behind” them. For example, there is a very brief discussion of the contents of the Guide to Judicial Conduct, but little or no analysis of how the code has been put into practice. Equally brief is the discussion of the contents of the 2012 edition of the Guide to Judicial Appearances before Select Committees. The lack of comparison of between the 2008 and 2012 editions of the Guide means that Blick misses important changes in how appearances before select committees are negotiated. These changes suggest that Lord Judge, the then Lord Chief Justice, had succeeded in tightening his control of how and when judges interact with Parliament. The chapter gives the reader no insight into how since 2005 senior judges have sought to recalibrate how judges and parliamentarians interact, with the changing content of the Guide to Judicial Appearances before Select Committees just one part of a larger constitutional story. Wholly absent from this chapter is any mention of the Concordat between the Lord Chancellor and Lord Chief Justice that was agreed in 2004 and that was so instrumental in smoothing the passage of the Constitutional Reform Act 2005. The Concordat would have made an interesting case study of how codes have been used to manage tensions between senior judges and ministers. On the one hand, the Concordat was the subject of intense negotiations, with Lord Woolf securing major concessions that in turn went some way to repairing senior judges’ confidence in the Blair Government. For several years after the 2005 Act, senior judges regarded the Concordat as a text of considerable constitutional importance. On the other hand, the Concordat was soon rendered partially redundant by the way that the 2005 Act made further fast-paced changes to the nature of judicial-political relations.

Overall, this book tackles an important and under-investigated topic in a manner that is sensitive to the history of parliamentary executive and the complexities of modern government. Although overly descriptive and repetitious at times, the book will be an especially valuable resource for lawyers studying the inner workings of the executive as well as for those keen to better understand parts of the UK Constitution that until recently remained largely out of sight.