In my point of view, the Constitution of England is one of the most important Constitutions to be studied, because, as we know, it is quite different from the others, breaking with some "dogmas" with which we are accustomed.
First because it is a historical and customary constitution. However, a very important observation must be made. Many books repeat a mistaken statement about the English Constitution - they say it would not be written. In fact, only part of it is not written. Many of the English constitutional norms are derived from customs and principles. But much of the constitutional norms are written. That is, it is not written in a single document, but part of it is written in different laws. Some of these laws are the Magna Charta (1215), the Petition of Rights (1628), and the Bill of Rights (1689). However, they are not written only in laws, but also in treaties, jurisprudence, and other types of written rules.
And this is so because, in reality, a constitution is the set of constitutional rules of a given legal order. For example, the Brazilian Constitution is the set of Brazilian constitutional norms, which are found in the document entitled Constitution of the Federative Republic of Brazil and in other texts. The Constitution of England, in turn, is the set of English constitutional norms, which can be found in any law or act, provided they are considered constitutional.
What happens is that the constitutional foundation of these norms is not explicitly written. That is, these norms are not textually, formally, declared constitutional. Explaining better, if we look at the Brazilian Constitution we will see that this (as well as most of the written constitutions) presents a preamble that declares the constitutionality of the norms inserted in that document. And the written rules themselves may also state that other norms are part of the Brazilian Constitution (such as some international treaties, constitutional amendments, and the Transitional Constitutional Provisions Act).
How, then, to know which English rules can be considered constitutional, if they seem to be in any law, and if there is no legal document that expressly declares them constitutional?
A legal norm is considered constitutional in the English system, if its subject matter, its content, has a constitutional nature, that is, whether it deals with the organization of state powers, or with fundamental rights and guarantees.
As we know, Constitutional Law is not confined to the study of legal norms, but to the constitutional system as a whole. So some aspects of the English political system are important to better understand this constitutional system.
The English laws have their origin in Parliament (composed of the House of Commons, the House of Lords and the Queen), and it is considered that all acts of Parliament are constitutionally legitimate (the constitutionality of their acts is not controlled), being, therefore, easy or flexible the possibility of changing constitutional norms. It is the principle of Parliament's Supremacy.
However, it is known that in reality the English system is extremely rigid, and its constitutional reform is very difficult, which is made gradually. This creates great political and legal security.
Another defining characteristic of Parliamentarism is that the national government is formed from Parliament: the leader of the party or coalition holding the majority in the lower house (the House of Commons) will be invited by the Head of State (the Queen) to form a government in her name. This leader then becomes the Prime Minister, and therefore, Head of Government.
The main body of government is the Cabinet, chaired by the Prime Minister (for this reason is sometimes called the President of the Council of Ministers). The members of this Cabinet are the main ministers (or senior ministers), who are essentially parliamentarians (possibly from any of the houses) and other citizens with relevant political capacity.
As a consequence of this training process, the government is politically responsible to Parliament. An example of this is that almost every week the House of Commons meets in a session called "Questions to the Prime Minister", in which the head of government (or whoever replaces him) should present an account of his performance and answer questions asked by the parliamentarians, both from ruling parties and from opposition parties.
Because of this political responsibility, if a member of the government loses Parliament's support (for example, if a finance minister fails to approve his annual budget proposal, or if another important matter for a minister is not approved), he will no longer be able to remain in his position, having no choice but to resign.
When there is a tension between the parliamentary forces in such a way that the ruling party, although majority, does not have a sufficient majority to approve its projects, the Prime Minister can request to the Queen to dissolve the Parliament and to call new elections. It is a way for the British to ensure that Parliament is a reflection of the will of the people, giving a new opportunity for the people to elect their representatives. This, however, obeys certain limits determined in Law.
In this way, we see that Parliament is the body that concentrates British political power - through the Legislative activity exercised in its two Houses, with the Queen's consent, and to compose and control the Cabinet.
Hence the principle and the fact of Parliament's supremacy, which means that everything that Parliament approves according to legal procedures is constitutional in the sense of being in line with the Constitution. If the Parliament approves a norm or act that contradicts the constitutional system, the phenomenon of unconstitutionality does not occur, but rather the reform of the Constitution.
This, however, is not something that trivializes constitutional reform, since, as we have seen, the English legal and social system is so solid that changes are made slowly and prudently - and it is also true, steadily, slowly and always.
History and Tradition
The English system is as it has been for centuries, but is also in constant transformation. The Magna Carta, for example, has recently completed 800 years. And although the English political system has changed a lot in the last eight centuries, these changes have been made gradually. The British Parliament as we know it today (with two Houses) has existed for more than 200 years. Constitutional norms are highly respected for the sake of tradition and custom.
It is said that the English Constitution is historical because its norms are created and changed historically, that is, it is necessary to go through a historical process so that the constitutional norms are changed. His study is a true study of Constitutional History, rather than of legal dogmatics as we are accustomed in Brazil.
Rule of Law
State authorities are now limited by constitutional rules. Unlike the Brazilian system that "creates" the State and its agents and which states the attributions of each one through the written Constitution, in the English system the constitutional norms limit the power of the State, starting from the assumption that before the State had unlimited powers (Absolutist State), which were gradually being limited, throughout history, according to need and convenience.
The British Constitutional Family
England, from the Modern Age, leads a United Kingdom, which now includes, in addition to England itself, Scotland, Wales and Northern Ireland. These three countries, in addition to electing representatives in the House of Commons and their nobles to sit in the House of Lords, also have their own political organization - a unicameral Parliament and a Government headed by a Prime Minister. England, however, does not have its own government, depending on the legislation and administration of the Parliament and Government of the United Kingdom.
The United Kingdom itself, until the beginning of the last century was a great empire, which was dissolving throughout the twentieth century. All British colonies and dominions were under the rule of the constitution of England. With the independence of the former colonies, most adopted their own writing constitutions. This is the case of India and South Africa, for example.
But some colonies and domains, on the other hand, remained (and still remain) having the Queen of England as Head of State, despite having their own Head of Government such as Canada, New Zealand, among others.
These countries, together with others, make up the Community of Nations, an international organization formed by former British colonies, and commonly called Kingdoms of the Commonwealth and are part of the English Constitutional Family.
In the Kingdoms of the Commonwealth, therefore, the English constitution still reigns. Each has its own Parliament, its own Prime Minister appointed by the local Parliament, just as it does in the United Kingdom. In each of the Kingdoms of the Community of Nations the Queen is represented by a Governor General, appointed by her.