Constitution is the utmost supreme law
British constitution it is an unwritten constitution but it does not mean that there are no written documents. According to Vernon Bogdanor characterised as follows:"The essence of the British constitution is … better expressed in the statement that it is a historic constitution whose dominating characteristic is the sovereignty of parliament, than in the statement that Britain has an unwritten constitution  ". British constitution is flexible the parliament can alter and repel the constitution at any time because of that flexibility the government can amend without any difficulty or any special procedure. The British
Constitution is a monarchy system the head of the state is Her Excellency Queen of United Kingdom Her Majesty holds prevalent formal powers under the royal prerogative, but presently these powers are traditionally exercised by the designated government of the day which is lead by the Prime Minister.
The British constitution consist with various kinds of history traditions and culture, constitutional acts, customs, political practices, conventions .According to the definition of A V Dicey “conventions, understandings, habits or practices which, though they may regulate the conduct of the several members of the sovereign power…are not really laws at all since they are not enforced by the courts. This portion of constitutional law may, for the sake of distinction, be termed the 'conventions of the constitution', or constitutional morality…"  Conventions are the most important part of the British constitution they are non legal sources of British constitution and if a convention is breach the courts cannot pronounce that it is unconstitutional or null-and-void Attorney General v Johnathan Cape Ltd  .
Even though the conventions do not have a legal value they are very much respected in a political base. As an example the political party which get the majority from the general election is always invited to form the government by Her Excellency the queen.
Another classic example to illustrate the political value of the constitutional convention, at the time of Iraq war Foreign Secretary Robin Cook resigned after failing to accept collective responsibility for the decision to commit Britain to military action in Iraq without international agreement or domestic support. Mr Cook could not back the governmental stance regarding the war with Iraq.
Furthermore, he publicly criticised the government's involvement in the campaign. With this in mind, conventional rules demanded his resignation. 
When we discuss about the evolution of the British constitution it drives back to 1215 the first formal documentary evidence about the British constitution Magna Carta came into action. This is the first formal document where the liberties, freedom and the democracy of the society were established by King John. The evolution of English constitution law started with Magna Carta followed by Petition of Right in1629, Treaty of Ripon in 1640. In 1688 as a result of the glorious revolution the conflict between the parliament and the king a new constitution emerge where the parliament took hold of the legislative supremacy by the Bill of Right of 1689. The below acts and treaties also can be taken in to account as the most fundamental parts of the British constitution, Crown and Parliament Recognition Act 1689, Act of Settlement 1701 ,Act of Union 1707 Act of Union 1800 ,The Parliament Acts 1911 and 1949, Life Peerages Act 1958, Emergency Powers Act 1964 ,European Communities Act 1972 , British Nationality Act 1981, Supreme Court Act 1981, Representation of the People Act 1983, Government of Wales Act 1998, Devolution Acts 1998, Human Rights Act 1998,House of Lords Act 1999 .
From the history to the present there are arguments, criticisms, proposals about the nature of the British constitution .The most discussed and debated argument was whether to convert the unwritten constitution in to a written constitution.
In 1997 Tony Blair’s and in 2010 Tories leader David Cameroons political propagandas were based on major constitutional reforms and constitutional arrangements. And both leaders got the majority votes and the consent for the policy change and the power to form governments this means that citizen of UK have no very much confidence on the present constitution.
According to the current situation there are two aspects to the question and we should look at the positive limbs of the constitution as well as the negative limbs. This means whether the flexibility strengthen the constitution or weakens the constitution and the effect of the unitary and monarch constitutional system. For this question firstly we should look at this flexibility effect the judiciary, executive, parliament, citizens and the democracy from the current constitution.
The debate is whether the present constitution is good as it is or should it be changed firstly absent of a written constitution affect the democracy of the British society as well as there is no certainty and because of the flexibility the parliament always change the constitution.
And the other fact is that the unitary constitution secures the parliamentary sovereignty of the United Kingdom. And also by that it secures the territorial integrity so by the meaning it says that there is no certainty in the British constitution, but from the unitary nature even though it is flexible no one can change the sovereignty which the Westminster exercise
When we consider about the devolution acts it clearly shows British current constitutional system is very live and on the other hand because of the unitary nature it has only given certain powers to Scotland, Ireland and Wales the most important facts like national security matter and fiscal matters external affairs matters solving powers are with Westminster parliament and the unitary nature directly strengthen the current constitution.
According to the theory of parliamentary sovereignty the parliament can entrench and alter or repel any act impliedly and expressly. On the other hand the parliament is supreme law making authority so the parliament can make or unmake any law what so ever on any subject matter and the courts have no control on those laws and they cannot claim that these law are unconstitutional this means that the current constitution have no legal value and it has no control over the parliament. The Prevention of Terrorism 2004 is incompatible with the Human Right Act of 1998 and the rule of law but because of the current openness of the constitution and the power that the parliament have, they set aside the constitutionalism and the rule of law.
On the other hand UK entering in EU 1972 this affects the British constitution because there is no rigid constitution to protect UK and to prohibit the UK parliament doing future actions which affect the parliamentary sovereignty.
As an example In 1972 UK entered into the European Union, and the British parliament brought forward the EU Act of 1972 with this act coming in to action as a law the conventional power of implied repel was abolished and also because UK entering to EU it affected the territorial integrity and from the drafted EU constitution it will effect a lot on the domestic law, will be set aside by the EU law and EU law will prevail. These constitutional arrangements will directly affect on the British constitution this all actions are results of the current openness of the British constitution.
There is a another argument whether the British government actually have a constitutional mandate to follow some of the parliament action even if there is not a specific mandate sometimes the government over go the constitution it means that parliament uses the ultimate lawmaking power over the constitution. This clearly illustrate that the constitution of UK is not clear and it does not separate the power properly between the governmental institutions. On the other hand the responsibility of the government is only vested by the parliament and the other institutions are ignored.
Because of the lack of a written constitution the judiciary of the UK always face a big problem the, judiciary of UK only have the power to interpret the laws which are created by the parliament and on the other hand there is another procedure of judicial precedent in common law the current constitution do not clearly define the separation of power between the institution. As a result of this situation it seems that there is no clarity in the present constitution. As a result of above mention imperfection the courts are unable to check and balance the parliamentary work.
And there is another problem there is no adequate procedure for amendments or formal procedure in 1911 a problem arise when the parliament brought the monetary bill so the parliament brought a new procedure instead of the manner and form procedure which is the normal procedure of passing an act, House Commons stage, House of Lords stage, Royal Assent an act to become a valid act the act should get the consent of both House of the parliament but the Parliamentary Act of 1911 ,1949 and the Hunting Act 2004 enacted avoiding the special parliamentary procedure. The above example clearly indicates that in present constitution there are no bars for informal modifications this is a major weakness of the current constitution.
The Sri Lankan government wants to change the constitution according to the current need of the country but to change the constitution is very hard because the constitution is very inflexible so the government cannot fulfil the needs of the society .unlike Sri Lanka the British parliament can change their constitution any time as a result of that when there is crisis or national emergency situations UK can easily protect their country from that threat. The Prevention of Terrorism act of 2004 and the Immigration Act of 2008, these two acts are classic examples to show the current openness strengthens the constitution.
Because of the openness it is very easy to entrench the constitution on the other hand it is very easy to modify according to the democratic needs of the society. So it is sensible to say that the British constitutional system indicates and reflect the changing circumstance and the changing world.
As a result of the openness of the constitution the labours that came in to power in 1997 brought the constitutional reform act which made some significant change in British judicial system they abolish some powers that Lord Chancellor had to protect the transparency of the judiciary, and to keep the separation of power alive.
On the other hand the repealing power protects the political secrecy and the national security and the territorial integrity because the openness of the constitution gives the right and the power to abolish any act any time. Other than the above mention statements the politicians are also protected by the openness cause if they promise a policy change prior to the election they must keep their word. This secures the certainty of the country as well as the individual opinions are valued because of the nature of the constitution.
Taking all the facts and the statements in to account my point of view is that the openness’ of the current constitution protect UK from each and every angle and it strengthen the constitutional values and constitutionalism, but it depends on the hand of the parliament to protect them and the judiciary to check and balance whether the parliament use this openness properly.