Theresa May announced, with unusual emotion, on Friday that she will resign as Conservative Party leader on June 7. While she will stay on as Britain’s prime minister until at least July, her time in office is now ending with an unfortunately lousy legacy. So, with the selection of a new Conservative leader, and by extension prime minister, about to begin, attention is rightly turning to the massive agenda he or she will inherit. First and foremost, this comprises tackling the damning legacy of May and David Cameron, which has seen the shambolic handling of Brexit, but also wider political drift, and the possibility of the UK itself unraveling. This leaves a huge in-box. The tragedy is that this troubled political inheritance was by no means inevitable, and results in large part from some of May and Cameron’s unwise decisions in office. On Brexit, for instance, the referendum that Cameron called was not one of necessity. This was compounded by his failure, before the 2016 plebiscite, to allow the civil service to conduct any planning in the event of a “Leave” win. Calling a referendum in these circumstances proved to be a reckless gamble that destroyed his premiership. And in the past three years May has failed to pick up the pieces and secure a domestic consensus around an EU withdrawal deal, exceptionally difficult as that task would have been for any politician. The referendum vote also had major implications for the longer-term future not just of the EU but also the UK itself. On the latter front, for instance, the UK’s current constitutional settlement has become further destabilized, with a significantly increased likelihood of a second Scottish independence referendum, for example. Unlike England and Wales, Scotland and Northern Ireland, too, voted to remain in the EU. This is a point constantly emphasized by parties such as the Scottish Nationalist Party (SNP), which favor further fragmentation of the UK.Unfortunately for unionists, the aftermath of the 2014 Scottish independence referendum has emboldened the SNP. Nicola Sturgeon, the Scottish first minister and SNP leader, has previously argued that the UK should exit the EU only if all four constituent parts (England, Scotland, Wales and Northern Ireland) individually voted to leave, an exceptionally unlikely scenario as she well knows. Should the leave vote ultimately lead to the UK leaving the EU under the next prime minister, which still appears likely barring a so-called people’s ballot which reverses the decision, it would increase the probability of a second Scottish independence referendum. Sturgeon has sought to lay the ground for such a post-Brexit plebiscite, and given the strong attachment that many Scottish people have to the EU, it is more likely than not that Scotland could vote for independence. For those who continue to favor a strong UK, these developments are immensely concerning, and the end result is likely to have ramifications not just for England, Scotland, Wales and Northern Ireland, but for the rest of the world, too. The fact is a weaker UK would no longer punch so strongly on the international stage, which would also adversely affect its ability to bolster international security and prosperity at a time when both remain fragile. Scottish independence would undermine the UK’s influence in multiple ways, including its voice in key international forums such as the UN, G7, G20 and NATO. As John Major, the former Conservative prime minister, has argued, the union would be perceived to be harmed “if a chunk of it voluntarily chose to leave ... the voice of Britain ... would be growing weaker because we would have had a political fracture of a most dramatic nature.” Perhaps most prominently, the breakup of the union could be seized on by some non-permanent members of the Security Council, and/or other UN members, to demand a review of the UK’s membership of one of the six principal organs of the UN. To be sure, reform of the Security Council is overdue. However, Scottish independence could see this issue being decided on less favorable terms for Britain than might otherwise be the case. Budgetary cuts forced by the loss of Scotland’s tax base could also affect the UK’s sizeable overseas aid budget, which promotes massive goodwill abroad. The UK is one of the world’s largest providers of international aid after the US, and is one of the few G7 states to adhere to an internationally agreed target of spending 0.7 percent of GDP on overseas aid. Moreover, a UK parliamentary committee has rightly warned that losing the Scottish tax base could lead to further spending cuts to the armed forces. Taken overall, the new Conservative leader will have to tackle as best he or she can the lousy legacy of May and Cameron. Key tasks will be resolving the Brexit shambles in the national interest and preventing the breakup of the UK. Failure to achieve these goals would diminish the nation’s international standing, adversely affecting its ability to bolster international security and prosperity.