Career civil servant Sir Tim Barrow, 53, became the UK's permanent representative to the EU in January. The promotion of the former political director of the Foreign Office to Brussels sent an important message to May's critics at home and abroad: Sir Ivan Rogers, his predecessor, was replaceable.

"A seasoned and tough negotiator, with extensive experience of securing UK objectives in Brussels, he will bring his trademark energy and creativity to this job – working alongside other senior officials and ministers to make a success of Brexit," a Downing Street spokesperson said.

Barrow's appointment was also welcomed by Shadow Brexit Secretary Sir Keir Starmer. "It is of course vital that there should be no vacuum in such an important role and that the new permanent representative should be someone with a strong and distinguished record of service as a diplomat," he said.

The father of four has enjoyed a 30-year diplomatic career. First joining the Foreign Office from the University of Oxford in 1986, he would later work in the British Embassy in Moscow between 1990 and 1993.

In this posting, Barrow would have seen the collapse of the Soviet Union and the rise of Boris Yeltsin, the first president of the Russian Federation, first hand.

Vladimir Putin, KGB-man turned politician, would later describe the fall of the Communist empire as "the greatest geopolitical catastrophe" of the 20th Century.

With Putin's provocations in Ukraine and the alleged Russian hacking of the Democratic National Committee's email systems ahead of the US election, expertise of the Kremlin is back in demand.

Barrow, who also served as the UK's ambassador to Russia and to the Ukraine, knows Moscow and Brussels well. Knighted in 2015, he was praised for being at the forefront of "managing the complex and important relationship between the UK and Russia during an unprecedented period".

"He has tirelessly promoted UK's interests, including on human rights, fostering cultural and education links between the two countries, and supporting the UK's scientific, trade and economic interests in Russia," the citation added.

But Barrow's extensive experience, which includes previous postings to Brussels, is not enough to get former Ukip leader Nigel Farage on side.

"Good to see that the Government have replaced a knighted career diplomat with.... a knighted career diplomat," the Eurosceptic firebrand declared.

Sir Tim Barrow
Russia's then president Dmitry Medvedev (R) speaks with Tim Barrow, Britain's ambassador to Russia, in Moscow in December 2011 Reuters