This week Kim Darroch, the UK's ambassador to the United States, was forced to resign after leaked diplomatic cables showed his negative assessment of Donald Trump. At issue here is not whether his view of Trump was accurate (diplomats are there to give their honest perspective to the government, it is up to the government how they use that information). Trump's reaction to the leaks, and whether his decision to completely cut off links with Darroch was proportionate, is also not the point. What is far more concerning is that the crisis that formed in the two countries' diplomatic relations was not an unfortunate accident - it was a deliberate political attack. Darroch was anti-Brexit and his view on the matter was known in political circles. So, in order to force him out, someone on the inside collaborated with Brexiteers in the media to leak the cables and create a dispute with the US President.Let's take a moment for that to sink in. This was a planned attack on an experienced ambassador. A diplomatic crisis with one of the UK's main allies was considered an acceptable vehicle for this attack, with seemingly no thought given to any long-term damage that could follow. And why? Because Darroch, having held apolitical functions in the UK's diplomatic service for almost four decades, was considered unfit as he held the wrong political views.And while some Brexit-leaning politicians did row in behind Darroch and supported the UK's right to not have its choice of ambassador be dictated by the US President, many did no such thing and chose to take Trump's side. Most notably the likely next Prime Minister and hardline Brexit supporter, Boris Johnson, repeatedly refused to support Darroch or condemn Donald Trump.How did we get to this point? How did we become a country where so much of the media and political class feels it is acceptable to coordinate political attacks on civil servants?The answer is not hard to find. Darroch's detractors have made it plain as day and the debate that followed once the cables were leaked featured this point prominently. This all comes back to the 2016 referendum and the mandate provided by the Leave vote. Or, more accurately, the way that mandate has been pushed and stretched to its breaking point.Steadily, but without taking a single step back, Brexiteers have used the referendum to claim a mandate for ever more extreme measures. First, this was to push for a hard form of Brexit as the only kind that would properly respect the referendum mandate, taking the UK out of the Single Market and Customs Union - already a distortion of the actual mandate that was given, far beyond what the close result should have allowed. Then court rulings, and the judges who issued them, that empowered Parliament, regardless of what Parliament may decide on the issue, were deemed to be a violation of the referendum mandate. Then the referendum was used to insist on No Deal as the only acceptable form of Brexit. And most recently, civil servants who do not pass the Brexit loyalty test are also set to be hounded out of their posts. By a series of incremental steps, Brexiteers have used the referendum mandate to declare a right not just to leave the European Union but to reorganise UK politics as a whole and to reorganise it according to their beliefs. It is not enough for the UK to be formally out of the EU, it must become a Brexit state through and through.It is time for the rest of the population to come out and say something clearly: the referendum result did not empower Brexiteers to make these changes. Indeed, beyond the specifics of the referendum campaign, the result could not have empowered such massive change. What Brexiteers are effectively trying to claim is that the 2016 referendum result not only allows them to implement a specific policy but rather it gives them a monopoly in controlling the UK's entire political system. They have sought to instrumentalise a limited mandate and turn it into an unlimited one. This claim is not only in violation of the reality of the referendum campaign and the ideas that people were being asked to vote on, it is a conception of the referendum mandate that is in direct contradiction with the fundamental tenets of liberal democracy.This has not come entirely out of the blue. Dominic Cummings, one of the architects of the Vote Leave campaign, has regularly expressed his desire to 'reform' the civil service, going back to before the referendum. Though the claim he makes is that he wants to see a civil service which is more efficient and more flexible, in practice his 'solution' to a civil service that does not always comply to his political worldview is to place the civil service, including the hiring and firing of individuals, under complete political control. A political control that would, naturally, also be dominated by Brexiteers. This is typical of the arguments Brexiteers are making about the civil service now in the context of Darroch's resignation. Though they argue it would be about restoring competence and ability, the fundamental test being applied at every turn is political loyalty - there's no explanation of how competence is ever assessed, beyond the extent to which civil servants are willing to act as yes-men to politicians (a system that any reasonable observer could determine would reduce rather than enhance competence). The final result therefore is a vision for a powerful executive controlling a political civil service. Combine this with the demands for a tame judiciary and a 'patriotic' press and the dangers become more than self-evident. These Brexiteers would only be satisfied by a political reorganisation that would effectively eliminate checks and balances. This is the authoritarian tendency of hard right populist regimes that we have seen develop across the world. It is the model of 'illiberal democracy' that Viktor Orbán has made his trademark. And we have seen the results of this kind of system. Far from enhancing or restoring 'true' democracy, it entails its destruction as executive power becomes overwhelming and uncontrollable.This fits perfectly with the populist conception of democracy more generally. The people are considered to have a single will and for democracy to be truly alive, that will must be able to act completely unimpeded. Politicians, once they have received a mandate, should be able to do absolutely whatever they feel is necessary to execute that mandate. Adding any constraints to this power is unacceptable as it is believed that these constraints would be obstacles to the democratic will of the people. This idea is of course entirely flawed. It does not leave room for legitimate opposition or the force of the law to limit the powers of the government. Without these factors, the best outcome is usually that government becomes corrupt and inefficient. The worst is that democracy is destroyed entirely.In seeking to claim a mandate that is so far removed from the original policy question, and which so clearly attacks the functioning of British democracy, Brexiteers have destroyed the meaning of the original mandate. The only option that is left is the conception of the mandate that they have created, a conception which cannot be tolerated, much less accepted. This is an idea that is so contrary to the basic idea of the UK as a liberal democracy that it can only be considered to be illegitimate - the referendum simply cannot have given this power because we would never have put such an idea to a vote in the first place. As such, as a result of their hubris, Brexiteers have destroyed any mandate at all. Much has been made of the need for losers' consent in a democratic system, yet equally important is that the winners are proportionate in the exercise of their mandate. In their zeal to not fall short of the policy direction that emerged from the 2016 referendum, Brexiteers have long ago abandoned this sense of proportionality. The first effect of this was that it removed the obligation on the losers to consent to the result. The second was that, in exceeding the scope of the mandate, Brexiteers violated it and rendered it void.Having established the illegitimacy of their position and the emptiness of the mandate they still claim, there is now a democratic obligation to prevent them from turning their vision into a reality. In a narrow sense, this would likely require stopping Brexit. In a more general perspective, there is a need to restore public trust in the apolitical institutions that Brexiteers have derided, to once again defend the importance of limitations on power and the vital role that opposition plays in holding government to account. This is true of the media and the judiciary. Equally well, political opposition is vital and an independent civil service that values expertise over political allegiance is a key part of any effective democratic state. Looking to the future, we must find ways to prevent this kind of situation from arising again - at the very minimum keeping referendums away from constitutional questions that are best dealt with by Parliament. In this process, do not be cowed by accusations that you are not respecting the referendum mandate - the mandate from the 2016 referendum is gone and it was Brexiteers who killed it.