Constitutional Conventions As A Source Of Rules
There has been a long held belief that the UK has an “unwritten constitution"  Philip Norton said that the UK constitution is partly written and L.J. Stephen Sedly believed it was descriptive. It is not based on a single codified source of law, but rather, resides in the form of statutes and common law and most recently European directives. Equally parliamentary conventions such as collective and individual ministerial responsibility and the Royal Prerogatives that include, the power to appoint and dissolve parliament. These principles are not recognized by law, however refusal to observe conventions may produce unwanted consequences, and as a result they are seen to be binding in nature.
These conventions form an integral part of the UK constitution, because they serve to regulate the day-to-day operation of government.
Conventions also act to stabilize the legal structure by supplementing pre-existing rules. Famously Sir Ivor Jennings said, “Conventions provide the flesh which clothes the dry bones of the law" 
What then are conventions? There is no one definition of what is supposed to be a convention, writers and scholars have agonised over this for decades. Dicey described them as “understandings, habits or practices which, though they may regulate the conduct of several members of sovereign power… are not, in reality laws at all since they are not enforced by the courts"  Marshall and Moodie spoke of them as being “rules of constitutional behaviour which are considered to be binding by and upon those who operate the construction but which are not by the law courts… nor by the presiding officers in the Houses of Parliament (1971,pp 23- 24)"  , John Stuart Mill called them “unwritten maxims"  , and author G. Ganz believed that conventions were more important than law when she said “the essence of the British constitution lies not in its laws but in its conventions"  . UK conventions span the entire constitutional system throughout the legislature, judiciary and the executive branches of government. Conventions are not laws they are regarded as imposing obligation on those to which they apply, any breaches of convention may lead to allegations of unconstitutional behaviour and are of great importance Dicey once said that “if conventions are broken, the law is not necessarily so, yet the breach may cause the law to change"  he went on to say that “conventions are rules of political practice which are regarded as binding by those to whom they apply but which are not laws as they are not enforced by the courts or parliament"  . What Dicey meant by this was that conventions were not set out in any statute and even though the courts would give recognition to some of the conventions there is no way in which they can be legally enforced, though they are readily heeded to, as the political implications and constitutional difficulties that would otherwise arise by ignoring them would bring any offenders into conflict with the law, this seems to agree with what Lord Wilson of Dinton said “Conventions are often as important as rules of law and can sometimes be more important, judging by the consequences of their breach"  .
Following the case of AG v Jonathan Cape (1976)  they were described as being “rules of practice which are accepted as binding by those to whom they apply, which are not set out in any statute and which are acknowledged, but not enforced by the courts"
Within the legislature conventions often relate to the ties between the House of Lords and the House of Commons, in the early 1900’s there was a convention that meant financial matters were to be dealt with by the House of Commons. However the Parliament Act 1911 was brought into power after the House of Lords breached this convention after rejecting a finance bill. As well as this there is the convention that makes sure that the Prime Minister is always the leader of the political party that has the majority in Parliament and is always a member of the House of Commons.
There are also conventions such as individual and collective ministerial responsibility, where it is accepted ministers have to resign from office if they loose the confidence of the House of Commons.
In terms of the judiciary, it is generally thought that judges do not take notice of political conventions, however, Marshall believed that there was an intrinsic tie between conventions and the law when he said “non-legal rules regulating the way in which legal rules shall be applied"  .
There have been many case examples where it can be seen that judges sometimes take convention into consideration and even use them as a basis for common law. The courts recognition of collective ministerial responsibility was given In the case of Liversidge v Anderson (1942)  Famously in the case of R v Secretary of State for the Home Department, ex parte Northumbria Police Authority (1989)  where the Police Authority believed itself to have exclusive power to equip the police force under S.4 (4) of The Police Act 1964 to which the court of appeal stated that the crown still had the prerogative power to do this “A prerogative of keeping the peace that existed in medieval times has not been surrendered by the Crown in the process of giving its express or implied assent to the modern system of keeping the peace through the agency of independent police forces (post, p. 58H)." 
Marshall described as
Perhaps one of the most important conventions is that of the Royal Prerogative, such powers include the royal assent. After both Houses of Parliament have passed a bill without royal assent it cannot come into power.
The power to appoint, this gives the monarch the right to appoint peers and make the leader of the majority party Prime Minister.
Blackstone described the Royal prerogative as “that special pre-eminence which the King hath, over and above all other persons, and out of the ordinary course of the common-law, in right of his real dignity."  From this Blackstone makes it obvious that the Royal Prerogative is of a legal nature though unique only to the crown.
Over time the power of the Royal Prerogative, has diminished. This is popularly believed to have been caused by the event commonly known as the “Glorious revolution" in 1688 and as a result the Bill of Rights was formed, and the then monarchy became a constitutional monarchy in which the monarch no longer serves as the sole source of political power in the state, legally bound by the constitution, and employs a parliamentary system
During this time the Articles 1, 2 and 4 of the Bill of Rights stripped most of the Monarch conventional power.
There is a vast difference between the Royal Prerogative power today and that of the 17th century. The most notable of which is the difference in the personal power of the Queen as most of the prerogative powers now reside with the executive branch of the Government.
Because of this Dicey set out to redefine what was known as the Royal Prerogative to make it more fitting for the modern day, as such he described the prerogative as “every act which the executive government can lawfully do without the authority of an Act of Parliament" 
However as Blackstone made clear the power resides with the Crown and is separate from law, this fact has been known to cause problems where laws overlap with contradictory prerogative powers, for instance the case of A-G v De Keyser’s Royal Hotel ltd (1920)  where the prerogative power of claiming property had been utilized with regards to the “defense of the realm regulations", the House of Lords held that any laws that contradicted prerogative powers were to take president, this approach is in keeping with the understanding that Parliament is supreme.
Not only are prerogative powers less potent, and fewer in number now more than ever, it also seems that no more prerogative powers can be made. This was shown in the case of
BBC v Johns (1989)  when Lord Diplock stated “it is 350 years and a civil war too late for the Queens court to broaden the prerogative. The limits within which the executive government may impose obligations or restrictions on citizens of the UK without any statutory authority are now well settled and incapable of extension". 
The prerogative power suffered a further amount of undermining in 1982 in the historic GCHQ case which arose during the cold war. Margret Thatcher, then Prime Minister, attempted to get rid of the Council of Civil Service Unions. This case however established the principle that the exercise of prerogative power was subject to review by the courts. For this reason many now believe that the Royal Prerogative power is on a par with statutory discretionary powers.  As well as that it can be said that for the first time in history there had been significant judicial check on the Royal Prerogative that represented a seminal moment in the development of the Royal Prerogative power.
Although past case law, parliamentary measures (statutes) and a civil war have acted to restrict and reduce the overall power and number of Royal Prerogative powers they do however allow the Royal Prerogative to adapt and evolve as was seen in the case of R v Secretary of State for the Home Department, ex parte Northumbria Police Authority (1989)  , in which a medieval prerogative power was adapted to suit the needs of the modern day.
When discussing the nature of conventions many felt that the lines between both the law and conventions have become blurred. This was an opinion held by both Sir Ivor Jennings and John Mackintosh. Indeed Jennings believed that there was no difference when he stated “there is no distinction of substance or nature"  . On the other hand Mackintosh believed that there was only a small difference between the two when he said, “the real difference between law and convention is just that there is no formal procedure for enacting or enforcing convention, though some conventions… are as important as any laws and perhaps even more difficult to alter"  however subsequent case law has acted to show this idea is overly dismissive, as can bee seen following the cases of A-G v Jonathan cape Ltd (1942)  and Amendment of the constitution of Canada (1981)  , where the insufficient amount of legal remedies came about due to the differences between law and convention, leading to the courts refusing to enforce convention. Therefore the courts now see conventions as entirely different to law; this view was expressed in the case of Manuel v A-G (1983) 
It is clear that the UK has a wide range of conventions that are derived from medieval sources that filter down through all levels of the government most important of which is that of parliamentary sovereignty, and the Royal Prerogative, however in modern times the exercising of these powers is often undertaken by ministers, with royal assent.
These conventions have had a positive influence over the development of UK society for greater freedoms and more evolution allowed the laws to more accurately reflect current climates.
The unwritten nature of conventions allows for much more freedom for evolution within the constitution in ways that written laws would make impossible, by allowing the constitution to adapt in circumstances that are constantly altering and giving the means to bring about a conventions adaptation.
This leads to some conventions developing over time whilst others are merely abandoned. However this ability to adapt and change is fundamental to an effective, modern constitution.
In conclusion the evidence suggests that constitutional conventions are a necessary and often vital part to a working constitution. They are not legally enforceable and allow for a degree of flexibility leading to greater changes and adaptations enabling constitution to keep up with a constantly evolving society. Conventions act to regulate numerous areas of the UK constitution and exist for every part of the constitution. Arguably the UK constitution could not operate with out constitutional conventions; this is because they limit the very wide legal powers of the crown with out the need for sweeping changes to the constitution. They also allow the constitution and the government to work more flexibly, and so more effectively. Conventions also act as another check on the government ensuring that it is accountable to parliament for any unconstitutional actions. And finally they ensure an effective separation of powers; this is because it prevents the judiciary from having an active role politics, therein preserving judicial independences.
Many believe that, as there is no effective check on the power of the different branches of government conventions steps in. This is achieved by keeping judicial independence, reducing the powers of the Monarch and through collective and individual ministerial responsibility ensures that the government can be held accountable to Parliament.
As such it is clear that conventions form an integral part of the constitution and their role within it is vital and must not be over looked.