The UK government said Sir IVAN resigned early so that a successor could be in place before negotiations start.
Sir IVAN, who was appointed to the job by David Cameron in 2013, had been expected to play a key role in Brexit talks expected to start within months.
Last month the BBC revealed he had privately told ministers a UK-EU trade deal might take 10 years to finalise, sparking criticism from some members of parliament.
He told them this was also the view of the EU’s other 27 member states.
