Theresa May will move quickly to find a replacement to represent the UK in Brussels amid calls from the Tory party to appoint a wholehearted Brexiter to the job – possibly from outside the civil service. Sir Ivan Rogers, the head of UKrep – in effect the UK embassy in Brussels – quit in frustration on Tuesday urging his fellow civil servants to provide impartial advice and stand up to muddled thinking. He also made clear that the UK not only lacks an agreed exit strategy, but also a coherent exit negotiating team.
May is due to trigger Article 50, the moment the talks formally start, in March requiring her to urgently recruit someone committed to the goal of Brexit, but also knowledgeable about how the labyrinthine EU works.
Eurosceptics believe the job description includes someone willing to consider the possibility of leaving the EU without a full deal on a future relationship with Brussels.
Some Tories have called for the Conservative MEP Daniel Hannan to be handed the job of negotiating the UK’s exit, but there is no shortage of Conservative ministers overseeing the talks process.
The head of the civil service, Sir Jeremy Heywood, will resist calls for a politician to be handed the plum post, although ambassadors have occasionally been appointed from outside the core civil service network.
Heywood will be aware that Brexit is putting the civil service’s reputation for impartiality under unprecedented threat, with calls from the Ukip leader, Nigel Farage, for a complete clearout of the “Europhile Foreign Office”.
Iain Duncan Smith, the former cabinet minister, accused Rogers of leaking against ministers and claimed he had lost the trust of Conservative politicians. There is no evidence that Rogers was responsible for the recent leaks, one of which appeared to damage his standing in Downing Street.
In that context, a decision to appoint someone from outside Whitehall would be seen as a vote of no confidence in the impartiality of the civil service. 
Traditionally, the head of UKrep post has come from the Foreign Office diplomatic cadre, but in recent years senior Treasury officials have been given the job, reflecting the importance of economic and budgetary issues inside the EU.
The task will require a knowledge not only of the thinking inside the commission negotiating team led by Michel Barnier, but also the possibility of driving a wedge into the EU’s surface unity by locating allies in key European capitals. It was argued, fairly or not, that Rogers would not look hard enough to insert those wedges, focusing too much on Germany and France.
The classic Foreign Office appointment would be Tim Barrow, the director general for politics and a former ambassador to Moscow. He has extensive experience in Brussels. Alex Ellis, the former UK ambassador to Brazil, has been appointed director general of the department for exiting the European Union (DExEU). He is due to start in January, when he will take on responsibility for the negotiation strategy and for relations with EU member states and institutions.