When it comes to whether the lives of British troops should be put on the line in Syria, Parliament is powerless to act, and the Prime Minister is accountable to no one. Unaccountable power and an unacceptable process of undemocratic decision making have crystallised why the UK’s archaic unwritten constitution is so problematic.

A convention is a convention - until it isn't

The convention for deploying UK troops - which was established in 2003 - is that Parliament votes on proposals. But of course a convention is a convention - until it isn’t. The debate raging is whether the Prime Minister should have stuck to this convention, and given Parliament a binding vote on taking military action in Syria, or whether she was right to make that decision herself.

Best capturing the sentiment of those who don’t believe parliamentary sovereignty applies in cases of military responses - or ‘war’, to be old fashioned - Johnny Mercer MP said that “we must never let Parliament inhibit our Prime Minister’s freedom of decision making”. In a 21st century democracy, is it really acceptable to cut MPs, as our elected representatives, and the scrutiny they bring with them, out of one of the most important decisions a country can make?

Too much power in too few hands

The notion of such centralised and unbridled executive control should be an alarming feature in any self-described democracy. It is even more alarming in the UK, where our unwritten constitution bestow substantial unchecked and ill-defined powers on the office of the Prime Minister. The origin of these powers can be traced directly to the despotic monarchs that once reigned the UK, and were either abolished or gradually handed to the Prime Minister as the UK evolved into a parliamentary democracy.

This lack of checks and balances isn’t normal, not by a long-shot. The UK stands out in the lack of accountability around our executive office’s war powers, and the sweeping nature of the royal prerogative powers of the Prime Minister. The fact the Prime Minister can make a unilateral decision about taking the UK into armed conflict, breaking an albeit recent convention, is rather breathtaking when considering that unlike many executive offices in developed democracies, the Prime Minister is not directly elected and therefore not subject to direct accountability by the electorate. Citizens of the UK cannot vote Theresa May out of power if they disagree with her decision to take the UK into a conflict. That is a decision strictly reserved for members of the Conservative party alone, or her constituents at a push.

The politics of intervention

We can speak of humanitarian motivations, of course, but this is also ultimately a political decision. Since May was installed as Prime Minister after the vote to Leave the EU in 2016, the success of the post-Brexit project has to a large extent been hinged on a continuation and development of the ‘special relationship’ between the USA and the UK. Any deterioration in this relationship would mark a huge blow to May’s reputation, and send a wobble through the UK’s post-Brexit saving grace trade deal with the USA. For May, there is a lot at stake in choosing not to ally with President Trump in military intervention in Syria.

So while there are moral arguments to make for and against intervention in Syria, so too are there political arguments for and against. It is precisely the multidimensional nature of this debate that makes the case so compelling that the buck should stop with Parliament. Far from Mr Mercer’s assertion that the decisions of the Prime Minister should be unchecked by Parliament, there is no better time for parliamentary sovereignty to be asserted than when considering if the lives of British soldiers should be put on the line.

Central to the very notion of a democratic society is the principle of collective responsibility, and it is the responsibility of the Prime Minister to hear the complexity of the debate, rather than insulate herself from alternative opinions. There is no easy answer and no easy decision when lives are at stake, but whatever decision is made should be subject to robust debate, deliberation and scrutiny. A decision of such magnitude should weigh not just on the executive, but on all members of our Parliament.

We need to codify all powers - not just war powers

Time and time again the unwritten rules and conventions of the UK’s constitution enable those in power to put even more power in their own hands. We have an election every five or so years and the occasional referendum, and in between that the UK is sleeping walking into a state that bears little resemblance to a democracy. If your elected representative in the House of Commons doesn’t get a say, that means you don’t get a say.

Parliament can hold as many votes and debates as it likes, and perhaps the Prime Minister might, after all, uphold the convention. But so long as decisions about military intervention are subject to the whims of the Prime Minister, without a codified constitution that imposes constraints on what are currently archaic and ill-defined royal prerogative powers, there will always be a next time.