Charlotte Leslie is Director of the Conservative Middle East Council, and was MP for the Bristol North West from 2010-2017.

In just days, Britain’s place in the world may be defined for a generation. Britain’s enemies will be watching closely. Will Ministers live up to their words? Crunch time is coming.

We suffer crunch-time fatigue. We have been bombarded by deadlines and crucial cross-roads for the last four years, and it is easy to be dismissive of yet another. But this one is not what you think. It is not about a No Deal Brexit. The implications are perhaps deeper than even this.

The Government may be facing its first major foreign policy choice to make as a non-member of the EU, and it will define how the world sees post-Brexit Britain. The very core of Britain’s international reputation may be at stake.

On or after July 1st, Israel’s controversial Prime Minister, Benjamin Netanyahu may begin an illegal unilateral annexation of up to a third of the Palestinian West Bank, in fulfilment of his recent election pledges.

This is Netanyahu declaring land outside Israel’s internationally recognised borders as its own. It is land that Israel captured from Jordan in the 1967 war and has since held under military occupation.

Make no mistake; this is illegal. The prohibition of unilateral annexation of territory acquired by force is recognised as a basic rule of international law by all international courts – including the International Court of Justice, and international institutions including the UN General Assembly and Security Council. Netanyahu’s plans violate two UN Security Council Resolutions – 242 (1967) and 2334 (2016).

However you dress it up, the uncomfortable truth is that these plans are as unlawful as Russia’s incursion into Crimea in 2014. For this, Russia was punished by the West with crippling sanctions. And it is even more clearly illegal than China’s aggressive island-building activities in the South China Sea.

But Netanyahu has an extraordinary ally: Donald Trump actually supports Netanyahu’s unlawful plan, despite the condemnation of the UN, and the concerns of many Israelis that such a provocative and illegal action will seriously jeopardise their safety.

So Britain’s choice is stark and brutally binary: Will we demonstrate to the world that we impartially uphold and defend the international rule of law and penalise this illegal act?

Or will Britain trade in its global reputation for lawfulness in exchange for keeping Trump sweet for trade? Will post-Brexit Britannia be known not so much for ruling the waves, as waiving the rules?

The pressure on the UK Government to waive the rules, and respond to this illegal act with just a few words of condemnation or regret will be intense. They will be anxious to foster the warmest possible relationship with  Trump as they seek a trade deal.

So while Boris Johnson admits “What is announced by Israel would amount to a breach of international law” and “ we strongly object to it”, in practice, the Foreign Office appears to have already watered down its response to Netanyahu’s plans, crucially dropping the stock phrase that any illegal activity “will not go unchallenged'” in recent weeks.

But if the pressure to waive the rules is intense, the consequences of Britain jettisoning its global reputation for upholding international law are more severe still. Talk is cheap. When law-enforcers announce that they no longer care about enforcing rules, not by saying nothing but by doing nothing, then the international rogues and criminals come out to play.

Recall the consequences of Barak Obama’s conspicuous retreat from following through on his word: in 2013, Obama’s “Red Line” on the use of chemical weapons in Syria turned into a pink smudge; he back-tracked on his pledge to use military force if chemical weapons were used. David Cameron had failed to gain a majority for supporting the US in a hurriedly recalled Parliament and, without the UK’s support, Obama stopped short of the promised military intervention.

Regardless of the rights or wrongs of military action, this backtrack from a ‘Red Line’ was a catastrophic moment for world security. The USA had just announced to the world that it was weak. And weakness is dangerous. The West’s enemies were emboldened. Weeks later, Russia stepped in to prop up the Assad regime, driving the regional agenda. Months later, Russia made its encroachment into Ukraine.

Six years later, the international rule of law is under even more threat. State and non-state actors disrupt global security with misinformation campaigns, cyber-warfare, funding non-state proxies in countries (including ours) and industrial espionage.

Britain boasts the oldest justice system in the world. The rule of law is still seen as quintessentially British value and our legal system is respected around the world. Fairness is perhaps our greatest international export.

Enemies of the rule of law will be watching to see whether a post-Brexit Britain’s commitment to a rules-based order can be bought out. They will be watching our actions, not our words.

If we impose sanctions on illegal acts by Russia, but waive the rules for friends, not only will we have betrayed the cause of a more secure Israel and peaceful region. We will have set a dangerous precedent when powerful enemies make further land-grabs under a conspicuously impotent international rule of law.

As Britain enters a new era, this one decision will define our new global role. Standing by the rule of law without fear or favour is surely a true expression of Britishness and sovereignty. What is self-determination if it is not our right to determine and do what is right?