TVC E. The United Kingdom’s ambassador to the European Union, Sir Ivan Rogers, has resigned.

Sir Ivan, appointed to the job by former Prime Minister David Cameron in 2013, had been expected to play a key role in Brexit talks expected to start within months, the BBC reports.

The government said Sir Ivan had quit early so a successor could be in place before negotiations start.

Last month the BBC reports that he had privately told ministers a UK-EU trade deal might take 10 years to finalise, sparking criticism from some MPs.

Ministers have said a deal can be done within two years.

Labour said Sir Ivan’s departure was “deeply worrying” and Prime Minister Theresa May must be prepared to listen to “difficult truths” about the likely complexity of the Brexit process.