Early diplomatic career (1986–2000)

Barrow joined the Foreign and Commonwealth Office (FCO) in 1986 and worked as a desk officer in the Western European Department from 1987 to 1988. He then did Russian language training for a year before taking part in the British Days Exhibition in Kyiv, the capital of Ukraine, in 1989. From 1990 to 1993, he was the second secretary at the British Embassy in Moscow, and then returned to London where he was head of the Russia Section in the Foreign Office for a year. From 1994 to 1996, he was private secretary to a Minister of State for Foreign Affairs. Barrow was then appointed as a first secretary of the United Kingdom Representation to the European Union, serving from 1996 to 1998, before returning again to London as a private secretary to Robin Cook, the Foreign Secretary.^[5][6]

London, Brussels, Kyiv and Moscow (2000–2017)

In 2000, Barrow was appointed as head of the Common Foreign and Security Department at the Foreign Office, and in 2003 was appointed as the assistant director of the Europe Directorate - External, including during the UK's presidency of the Council of the European Union in 2005. He was also involved in negotiations over the Treaty of Lisbon at this time.^[7] Barrow served as deputy political director at the Foreign Office from 2005 to 2006 before his appointment as Her Majesty's Ambassador to Ukraine in 2006. He took up the post in July that year and held it until 2008 when he returned to Brussels as UK Representative to the Political and Security Committee and Ambassador to the Western European Union.^[5][6]

Barrow presents his letter of credence to Dmitry Medvedev, then-President of Russia, on 7 December 2011.

In August 2011, Barrow was announced as Her Majesty's Ambassador to the Russian Federation, to succeed Anne Pringle in November that year.^[5][8] Shortly after his arrival, he oversaw the visit of David Cameron, the Prime Minister, to Russia. This was part a wider policy implemented by Cameron for a "reset" in relations with Russia following the fallout of the poisoning of Alexander Litvinenko.^[7] In August 2012, he was summoned to the Russian Foreign Ministry over the stoning of the Russian Embassy in London by anti-war activists protesting Russian involvement in the Syrian Civil War.^[9] Deputy Foreign Minister Sergei Ryabkov expressed his wish to Barrow that "such dangerous and provocative actions will be strongly suppressed by the British security in the future."^[10]

In February 2015, following the murder of opposition politician Boris Nemtsov, Barrow hosted the former Prime Minister John Major. He also attended Nemtsov's wake with Major and joined other Western ambassadors in laying flowers at a tribute to him near Red Square. Politico reported that he was a "low-key" ambassador, which allowed him to avoid some of the vilification aimed at other Western diplomats. However, this masked some significant achievements that he made in a tenure marked by Russian military interventions in Ukraine and Syria and a crackdown on dissent by Vladimir Putin. Aleksey Pushkov, who led the State Duma foreign affairs committee during Barrow's tenure, commented that "He created the impression of a real professional who was able to advocate the positions of his own government, while also striving to find out and understand Russia’s positions."^[9]

After leaving his role in Moscow, Barrow was appointed as a political director at the Foreign Office in London, succeeding Simon Gass.^[11] This role included overseeing international organisations, multilateral policy, Eastern Europe, the Middle East and North Africa, Africa, South Asia and Afghanistan.^[6]

Permanent Representative to the EU (2017–2020)

On 3 January 2017, Ivan Rogers resigned from his position as Permanent Representative of the United Kingdom to the European Union, citing frustration over the government's negotiating strategy in their planned withdrawal from the European Union.^[12] The next day, Barrow was appointed to replace him. A Downing Street spokesman said Barrow was "a seasoned and tough negotiator, with extensive experience of securing UK objectives in Brussels."^[11] Charles Crawford, who worked with Barrow in the early 1990s, commented that he "understands Brussels and the EU, but he is not pickled in its ghastly processes."^[13] The Financial Times reported that Barrow's appointment was opposed by Oliver Robbins, the permanent secretary at the Department for Exiting the European Union, who wanted to take control of negotiations with the EU himself. However, the Foreign Office overruled him.^[14]

Barrow appointed two senior civil servants to his team in Brussels in March 2017. They were Katrina Williams, a director-general at the Department for Business, Energy and Industrial Strategy who was appointed as deputy permanent representative, and Simon Case, Principal Private Secretary to the Prime Minister, who was appointed as head of the UK-EU Partnership.^[15] On 20 March, Barrow appeared before the European Scrutiny Committee to give evidence on UK-EU relations prior to the invocation of Article 50. During the hearing, he warned that it may not be possible to leave the European Union without paying anything, as some Conservative MPs had suggested, and that "other legal opinions" offered "a different interpretation".^[16][17]

Barrow was responsible for handing over the letter of United Kingdom's invocation of Article 50 of the Treaty on European Union in Brussels on 29 March 2017 to European Council President Donald Tusk.^[18][19]

On 17 October 2018 Barrow accompanied British Prime Minister Theresa May to the European Council summit in Brussels, where 27 EU leaders met to discuss the Brexit negotiations (Art.50).^[20] After the Council meeting, Barrow wrote to the Secretaries General of the Council and Commission of the European Union on behalf of the UK. His letters stated that the UK had no doubt over its sovereignty of Gibraltar, including British Gibraltar Territorial Waters, and that Gibraltar's sovereignty would never be transferred against the democratically expressed wishes of its citizens.^[21]

Ambassador to the EU (2020–2021)

After the UK left the EU on 31 January 2020, Barrow's portfolio changed to British Ambassador to the European Union effective 1 February, being succeeded in 2021 by Lindsay Croisdale-Appleby.^[22]