The chances that the U.K. will make a disruptive break from its biggest market have grown with the resignation of the British envoy to the European Union, an experienced Brussels insider who was reviled by leading Brexit supporters. Ivan Rogers quit as Britain’s permanent representative to the 28-nation EU urging officials working for the U.K. in Brussels to keep challenging “muddled thinking” from colleagues in London. He warned the government lacked experienced negotiators and called for stronger working relationships between Prime Minister Theresa May’s London-based team and the U.K.’s permanent post in the Belgian capital. Supporters of as close EU ties as possible bemoaned his departure as a “body blow,” while backers of a clean break from the bloc cheered his going as a sign the U.K. government is committed to regaining complete control of immigration, laws and budget—even if that means fraying trade ties. “Britain’s partners will take this as a sign that May’s government is heading for a hard Brexit which puts sovereignty ahead of economic integration with the EU,” said Charles Grant, director of the Centre for European Reform. The prime minister needs to be told the “uncomfortable” truth about the difficulties of negotiating Brexit, Rogers said in a message announcing his resignation to staff in Brussels on Tuesday. “I hope you will continue to challenge ill-founded arguments and muddled thinking and that you will never be afraid to speak the truth to those in power,” Rogers said in the note, obtained by the BBC and published on its website. “The government will only achieve the best for the country if it harnesses the best experience we have.” Rogers’s comments show the size of the task facing May’s government less than three months before she is due to trigger the formal start of Brexit negotiations. He is the most senior figure from the U.K.’s politically neutral civil service to voice concerns over preparations for the talks. Political Minefield Dismissed by Brexit hardliners as an EU fanatic, Rogers was viewed by advocates of a softer form of Brexit as an experienced asset with strong diplomatic contacts and an openness to find common ground. His sudden exit at such a delicate juncture signals a hardening of positions, raising the chances the U.K. will quit the single market and revert to a tariffs regime. Last month, May’s office was forced to downplay remarks attributed to Rogers saying that it could take a decade to negotiate a free-trade deal with the EU. Her spokesman clarified that Rogers was merely communicating to London the views of other EU governments. The episode showed how his observations, however nuanced, inevitably risked exploding when they landed in the political minefield of Brexit. Read here about what makes a ‘Hard Brexit’ Versus a soft one. On Tuesday, May’s government said Rogers was scheduled to depart at the end of his term in November but had resigned early to enable a replacement to be appointed before exit negotiations begin. In his note to staff, Rogers outlined concerns about shortcomings in preparations for the talks. “Senior ministers, who will decide on our positions, issue by issue, also need from you detailed, unvarnished—even where this is uncomfortable—and nuanced understanding of the views, interests and incentives of the other 27” member states of the EU, he wrote. ‘Rapid Resolution’ The structure of the U.K.’s negotiating team needs “rapid resolution” and the “working methods” to create a seamless process between London and Brussels need strengthening, Rogers warned. “Serious multilateral negotiating experience” is “in short supply” in the U.K. government—unlike in the European Commission, which will lead the EU side in the talks, he said. In a thinly-veiled rebuke to Brexit-supporting politicians, he added: “Contrary to the beliefs of some, free trade does not just happen.” It will depend on the terms of the deals that the U.K. can strike, he said. “I shall advise my successor to continue to make these points.” Clean Brexit Rogers’s resignation fueled the view the U.K. could opt for a full break with the EU’s single market and customs union. His successor will play a leading role in May’s negotiations with the bloc and the choice will offer further clues on the direction of talks. “There are plenty of other civil servants, and they don’t have to be absolute advocates of leaving the European Union, they simply have to accept when push comes to shove, they must deliver on that mandate to leave the European Union,” former Work and Pensions Secretary Iain Duncan Smith, a prominent campaigner for Brexit, told BBC radio on Wednesday. Former U.K. Independence Party leader Nigel Farage said he welcomed the resignation and called for a “complete clear-out” of the Foreign Office, which has traditionally been seen as sympathetic to EU membership. Peter Mandelson, a former European trade commissioner, described Rogers’ departure as “a serious loss.” With the debate between a hard and soft Brexit raging on, it’s not just about the degree to which trade ties will be maintained but about how quickly the process can be completed. More pro-EU voices tend to say an exit cannot be rushed and will get tangled in a legal web of regulation minutiae. “Ivan was a rare voice of wisdom and sanity in all this because he knew what the stakes were,” said Paul Adamson, chairman of the Brussels-based Forum Europe. “The picture is much more confused now; much more complicated.” Pro-Brexit Conservative lawmakers like John Redwood disagree. He told the BBC he thinks the “task is pretty straightforward.” For him, whoever takes over from Rogers should head into battle sharing that assessment.