The utilitarian case for the monarchy is not about pageantry, deference  or the vulgar belief that it is worth keeping because it acts as a tourist magnet. It is not about the cost of the monarchy compared with a president. It is not about whether the individual members of the Royal family are worthy beings or if its very  existence is an insult to ideas of politically correct equality. The utilitarian case is purely political: our monarchy underpins Parliamentary government.

In resisting the abuse of the many by the few, Britain begins with the great advantages of a parliamentary system and an in practice non-executive head of state chosen by a means utterly outside political manipulation short of the outright  criminality of murder,  blackmail,  illicit threats and bribery, namely birth. These provide a massive barricade against a Prime Minister who would be a despot. He cannot act without the support of an elected parliamentary majority. His cabinet in practice must be overwhelmingly drawn from elected politicians. He may change his cabinet but he cannot do so without regard to a cabinet member’s status and popularity within the party on whose support he depends.

Most importantly, the prime minister (or any other politician) cannot become head of  state.  This is of central importance, because whether the powers of a president be executive or ceremonial, the mere   existence of the office of president provides an avenue for those who would subvert parliamentary control of the  executive. The example of De Gaulle in France
in the early years of the Fifth Republic demonstrates how easily a President’s powers may be extended by the overtly democratic means of a referendum against the wishes of a Parliament.  As things stand, a would be British dictator would have to do one of two things. The constitutionally legitimate path would  require him to first persuade Parliament to
adopt the idea  of an executive  presidential system and  then win the  backing of the electorate for a change to a presidential  system either through a referendum or an electoral mandate.  His illegitimate path would consist of either a referendum  put to the country against the wishes of Parliament or an outright coup backed by the military and police.

This is not to say that a prime minister equipped with a large majority cannot have a great deal of freedom  and personal power.  Both Thatcher and Blair achieved this. But however big their majority or great their personal authority they could not routinely make policy without some regard to the wishes of their ministers, backbenchers and the electorate. Whatever dark thoughts Thatcher may have had about  mass immigration or membership of the EU, she was in practice hamstrung in doing anything about it  by the opposition of powerful ministers  such as Nigel Lawson and Geoffrey Howe.  Tony Blair’s desire to severely reduce the welfare state was thwarted over many years by his Chancellor Gordon Brown.   To those leashes on their dictatorial desires can be added the fact that both Thatcher and Blair left office before they wanted to as a result of dissent amongst their parliamentary parties.   Had either been an elected president  operating outside parliament,  neither would have been removed before the end of their term of office.

A parliamentary system such as that of Britain has other restraints on abuses of power. First-past-the-post elections based on constituencies means that  MPs are not solely beholden to their party elite s as is the case with a party list system, and general elections, at least  since 1945, have normally produced a single party with a majority in the House of Commons.
This latter fact  means that the vast majority of modern British government have not been able to fail to honour their manifestos on the grounds that they  were part of a coalition.

If a demand for a president arose in  Britain  there would be an opportunity for those pressing for such a change to seek an executive president  with the executive removed from Parliament on the grounds that it was “more democratic” and provided a check on the power of the executive. . Anyone who thinks this is a good idea should look at the American experience where the powers of the president are constrained by a division of powers outlined in a written constitution administered by a supreme court. The President appoints his cabinet subject only to the agreement of the Senate, the President’s nominees being normally accepted.  Supreme Court judges are also nominated by serving presidents and vetted by the Senate.  These nominations   meet more Senate opposition, but most of those nominated are passed and if one is rejected, the President still gets to nominate an alternative.  That means a president  will broadly speaking get a judge into the court who is sympathetic to the president’s political views. As Supreme Court judges are elected for life,  a president
who is able to get even two new judges onto the court may affect its political bias for decades.

Even if a supposedly non-executive president was adopted with the executive remaining in Parliament,   the relationship between the prime minster  and head of state would be different. If the president was elected, there would be a second font of democratic authority regardless of the president’s powers. This would mean that there would be a constant temptation for a powerful politician to get themselves or a stooge elected to the presidency and then use their control  of Parliament to increase the president’s powers. If the president was simply appointed by politicians  a prime minster with a large majority could either take the presidency themselves and use his parliamentary control to increase his powers or place a stooge in as president, use Parliament to increase the presidential powers then control the stooge.

None of this is to pretend that the British system of government is perfect for the executive  has  found many ways of thwarting proper parliamentary oversight and control . The way it does this is fivefold (1) the entanglement  of  Britain in treaties, most devastatingly those related to the EU,  which remove sovereign power from not only Parliament but Britain; (2)  the increasing grip of party elites on the selection of candidates for Westminster seats, something of particular importance with the rise of the career politician who has never done
a job outside of politics; (3) an ever swelling use of secondary legislation, particularly statutory instruments,  which provide  much less opportunity for parliamentary scrutiny than primary legislation; (4)  the increasing appointment  of peers as ministers and non-politicians as “Tsars” for particular policy areas and   (5) the use of the Royal Prerogative by prime ministers.

There are ready cures for these ills. Treaties could be repudiated to regain sovereignty; the power of selection of Parliamentary candidates invested  solely  in local constituency parties would greatly reduce the power of  party elites;  a requirement that a Parliamentary candidate should have ten years  work experience unconnected with politics before being able to stand for Parliament would end the career politician; withdrawal from the EU would greatly reduce the amount of secondary legislation and increased time to scrutinise what was left and the use of peers and non-politicians banned.

That leaves the Royal Prerogative which represents  a particularly danger to democratic control because the powers exercisable under it are large. This is because of the long, organic
development of the relationship between Parliament and the Crown, the powers and rights of the Crown are little circumscribed by law, although most, and all the important ones, are now invested in practice in the office of PM. The dissolution or proroguing of Parliament and the calling of elections are by the prerogative. The PM and his ministers are appointed by
the Crown.  In principle, the monarch could appoint a Government in which none of its members sat in Parliament. No Bill can become a law without the monarch’s signature. Treaties and the making of war and peace can and are made without the assent of Parliament. All foreign relations are in principle within the monarch’s remit.  Justice is the monarch’s. The Monarch can do no wrong. Many senior state appointments such as appointments to the higher judiciary and bishoprics are one by the prerogative.  The monarch is head of the armed forces. There is prerogative power which allows the Crown to expropriate or requisition private property (with proper compensation) in time of war or apprehension of war. The Crown has limited powers of legislation under the prerogative, principally as respects the civil service and UK dependent territories.  This legislation is made by  Orders in Council, ordinance, letters patent and royal warrant. A ragbag of other rights such as treasure trove  and bona vacantia (the reversion to the Crown of property where there is no inheritor) and arcane rights such as the monarch’s right to (most) swans also exists.

The simplest thing would be  to cancel all prerogative rights which have a serious political dimension. This would reduce greatly the power of the PM and consequently  pass power to Parliament.  Such powers as are left to the monarch  should be laid down clearly in law. That would do a great deal to increase the power of Parliament and the ordinary member.
However,  more could be done without producing a situation which would leave a Parliament with an executive unable to act.  I would ban the whipping of MPs,  restrict the size of government to reduce the government “payroll vote” ( modern governments draw in more than 100 MPs) and make  the justice system truly independent by removing the political officers – Lord Chancellor, Attorney-General and Solicitor-General  – from the process of justice.

The banning of whips would not mean a government with a working  majority was constantly defeated because most party members will vote for their party programme. Governments would have to get used to accepting the odd defeat on even important policies as a fact of life not a cause to call a motion of confidence.  The reduction of the “payroll vote” would lead
to more independent minded backbenchers who would see  being a backbencher as an honourable and worthwhile end it itself.  The removal of the politicians from the process of justice is necessary to observe natural justice.

Two other things would be s desirable as a check on the executive: a written constitution designed not to promote a political agenda but to protect democratic control and prevent governments from undertaking anti-democratic policies or reckless behaviour which self-evidently will be damaging to the country.  If there is a Supreme Court to administer it, judges should be selected for a fixed period of five years and chosen by a free vote of the Commons. Alternatively, the administration could be done by a reformed second chamber (see below).

The second thing is electoral reform.  To address the problem of parties with even  less than 40% of the popular vote ending up with large majorities,  for the Commons  I would suggest double member constituencies  with each elector having a single vote. The two candidates  receiving the most votes in each constituency  would be  elected. This would probably  both reduce the size of majorities whilst giving any elector a choice of two MPs to go to rather than one.

As for the Lords, if you want a house which will not engage in a democratic mandate war with the Commons or simply replicate the party dominance of the Commons, I suggest selecting a house by lot from all those who put themselves forward to serve a single term of ten years, sufficient time for them to become proficient as a revising chamber.