Sir Ivan Rogers predicted much of the talks would be "conducted very publicly" with "name-calling" and an "extremely feisty atmosphere".
He added that EU Commission chiefs were saying the UK should pay 40-60bn euros to leave and thought a trade deal could take until the mid-2020s to agree.
He added that EU Commission chiefs were saying the UK should pay 40-60bn euros to leave and thought a trade deal could take until the mid-2020s to agree.