Downing Street has described the UK's new ambassador to the European Union, Sir Tim Barrow as a "seasoned and tough negotiator", who will bring "energy" to Brexit talks.
Barrow takes on the role as discussions with the EU are expected to start soon and promised to work for the "right outcome".
He replaces Sir Ivan Rogers, who quit earlier this week, accusing ministers of "muddled thinking".
Some Members of Parliament have accused Sir Ivan of being "half-hearted" towards Brexit.
Meanwhile, Prime Minister Theresa May is expected to give what is being billed as a "major" speech on Brexit within the next few weeks.