The first foreign official JD Vance met with after he returned from peace talks with Iran in Islamabad this week was not a diplomat or foreign policy official – it was David Lammy, the UK’s justice secretary and deputy prime minister.

Lammy will follow his trip to Washington, where he saw the vice-president and the secretary of state, Marco Rubio, with another to Barcelona, where he will represent the UK at a conference of global progressives, and then one to the Gulf.

The whistle-stop diplomacy from the former foreign secretary has prompted questions in Whitehall over who is really driving the government’s foreign policy at a time when it is more important than ever.

“Obviously the prime minister is in charge of the government’s foreign policy, especially when it is so important domestically as well,” said one government official.

“Beneath him though there are quite a lot of people all of whom are doing slightly different jobs and who think of themselves as the real foreign secretary.”

Keir Starmer conducts much of Britain’s diplomacy himself, and will co-host an international summit on how to free up shipping in the strait of Hormuz this week alongside the French president, Emmanuel Macron.

Yvette Cooper, the foreign secretary, meanwhile, has spent much of 2026 abroad, including trips to Washington, Ukraine and Saudi Arabia.

Cooper spent Wednesday in Berlin at a conference on the war in Iran, where she was joined by two other ministers on separate missions. John Healey, the defence secretary, was in the city to talk to counterparts about Ukraine, while the Cabinet Office minister Nick Thomas-Symonds was there to discuss the government’s attempts to forge closer EU relations.

Jonathan Powell, Starmer’s national security chief, joined the prime minister on his recent trip to the Gulf and remains his most trusted adviser on foreign affairs.

“Jonathan is the most significant influence on Keir’s foreign policy thinking,” said one senior government aide. “The two of them are similar in the way they prioritise diplomacy.”

Others also play an important role, including Varun Chandra, Starmer’s chief business and trade adviser, who was shortlisted for the role of US ambassador and maintains a good relationship with Howard Lutnick, the US commerce secretary.

Hamish Falconer, the Middle East minister, has a particular job selling UK policies to partners in the Middle East and to important community groups in the UK.

Emily Thornberry, the Labour chair of the foreign affairs select committee, said: “Foreign policy has never been more important in my lifetime – it is essentially domestic policy these days. That means there is more than enough work to be done, whether that is by Jonathan Powell, David Lammy, Yvette Cooper or the Foreign Office more generally.”

As for Lammy, he has kept a foreign policy brief even after being moved out of the Foreign Office and into the Ministry of Justice.

His role, say allies, is to foster relations with other deputy leaders, including in Europe where they often represent another party in a coalition and so can be important conduits. When he travels to the Gulf he will be talking to countries Starmer did not have time to visit on his recent tour.

Chief among Lammy’s relationships is his bond with Vance, with whom he struck up a friendship when the pair were in opposition. Those close to them say the two share many things in common, including an impoverished background, a love of writing and a strong Christian faith.

Over the course of a 45-minute discussion in the White House on Monday, the two talked about the direction of the peace talks and how the UK and US could collaborate on freeing up shipping in the strait of Hormuz, according to people briefed on it.

They added that Lammy did not have a specific request to make of his counterpart and was as interested in hearing about the Islamabad talks as anything else.

With relations between Starmer and Trump strained, many in government believe Lammy’s relationship with the powerful vice-president could be vital.

“It is the warmest bilateral relationship we have right now,” said one. Another added: “It is significant – it is a real channel of communication.”

Some in government see Lammy’s strong US ties and his frequent foreign travel as a challenge to the authority of his successor, Cooper. The foreign secretary is due to travel to Japan later this week, rather than the US or the Gulf, where much of the government’s international activity is focused.

Cooper has refocused the Foreign Office since she took over, telling officials to prioritise work on fragile and conflict-affected states, humanitarian assistance, tackling violence against women and girls and combating global health threats.

She has also worked on getting European allies to cooperate on attempts to curb irregular migration, a focus she brought with her from her time as home secretary.

Cooper speaks to Rubio once a week, and met the US secretary of state in Washington in February.

To a large extent, say government sources, the most significant foreign policy official in the British government depends on what is on the agenda.

When Starmer was working towards a trade deal with the US, Chandra became a close confidant. When he has sought to improve relations with Beijing, he has relied on the diplomatic skill of Powell. Now that the US relationship is being questioned, Lammy’s relationship with Vance has become a vital line of communication.

“Right now, when what is happening in the US and Iran is having such an impact on Britain, we need to take advantage of every connection we have,” said Thornberry.