A sacking in Whitehall is revealing the strain Brexit has put on the United Kingdom’s foreign policy. British Prime Minister Theresa May fired Defense Secretary Gavin Williamson on Wednesday over leaks to the press of conclusions from a British National Security Council meeting in late April. According to the leak, the British government had decided in the meeting that it would allow Chinese telecommunications firm Huawei to provide “non-core” components for the construction of the U.K.’s 5G mobile infrastructure. The NSC’s decision sparked immediate outcry from critics of the decision in the U.K. and U.S. officials who have been urging allies to shun Huawei technology. In a statement, Williamson denied that he had played a role in the disclosure.

Whoever leaked the Huawei decision likely hoped the backlash would force the government to reverse course and ban Huawei. A known China hawk, Williamson caused a diplomatic tiff with Beijing in February when he said the first deployment of the new HMS Queen Elizabeth aircraft carrier would be to the Pacific and that the U.K. needed to demonstrate its willingness to use “hard power” against China and Russia. In response, the Chinese government canceled British Chancellor Philip Hammond’s planned visit to China.

More important than who leaked the decision, though, is what the discord within the British government says about the limits of British strategic flexibility. A year before the 2016 Brexit referendum, the British government had launched a deliberate campaign to improve ties with China. During a visit to Beijing in 2015, then-British Chancellor George Osborne hailed the start of a golden era in U.K.-China relations and set a goal to make China the U.K.’s second-largest trade partner by 2025. In March 2015, the U.K. caused outrage in Washington when it became the first Western country to join China’s Asian Infrastructure Investment Bank. The same year, the U.K. and China signed nearly 40 billion pounds (worth $60 billion in 2015) in bilateral trade deals.

When May took over as prime minister, she tapped the brakes on the golden era. Just weeks into her premiership, May delayed one of the most significant of those bilateral deals – plans for China’s General Nuclear Corporation to buy a 33 percent stake in the 20 billion pound Hinkley Point nuclear power project – so that her government could review the contract. During her first official visit to China in February 2018, May raised concerns about sensitive issues like intellectual property theft and steel dumping, and she refused to endorse China’s massive Belt and Road Initiative.

But in the age of “global Britain,” when the U.K. is downplaying the importance of ties with Europe in favor of the rest of the world and aspiring to free trade agreements with major trade partners, including China, May’s initial position was untenable. There’s been no sign of backtracking on the (unofficial) Huawei decision, even after the U.S. repeated its threat to cease information sharing with countries that use the Chinese firm’s 5G technology. And last week, Hammond offered “British project design and legal, technical and financial services expertise” to help China “realize the potential” of the BRI, even after the U.S. criticized Italy’s decision to sign a memorandum of understanding related to the project.

To be sure, countries around the world are searching for the appropriate balance in relations with the U.S. and China at a time when they are increasingly competing for influence. Countries like the U.K., Germany and France have some strategic flexibility lent by economic heft and a degree of physical isolation from the two powers, separated as they are by an ocean from the U.S. and by Eurasia from China – a position few others enjoy. But only London is facing the possible exclusion from a customs union and single market with its largest trading partners, forcing it to curry favor with countries like China in case it needs a rapid trade deal to make up for lost revenue. It’s London that is under domestic political pressure to demonstrate to voters that it can thrive on its own without the European Union. If Germany or France – who, unlike the U.K., aren’t actively seeking a trade agreement with Beijing – want something from China, they can call on a bloc with a combined economy larger than China’s to speak for them. If the U.S. wants to withhold a trade deal from one of them, it has to give up its aspiration for a deal with the EU – something the U.S. president has wanted for a while.

A year ago to the day of Williamson’s firing, the chairman of the pro-Brexit European Research Group, Jacob Rees-Mogg, wrote that without the EU, the United Kingdom could “build a truly special relationship” with the United States. British Trade Secretary Liam Fox said last November that Brexit gave the U.K. the rare opportunity to raise the “special relationship” with the U.S. to a new level. The problem now is that to do so, the U.K. must choose a side: It can’t have a super special relationship with the U.S. and a golden era with China at the same time. The U.K.’s eventual exit from the EU means Britain won’t have to take orders from Brussels, but it also means balancing between Washington and Beijing will be more important than ever. The deeper the strain in those relations, the less freedom Britain will have in its foreign affairs.