It has been dubbed “the posting from hell”, but if anyone can bring a semblance of unity to America’s bewildering network of competing spy agencies, it is John Negroponte, the British-born career diplomat who was appointed director of national intelligence by George W Bush last week.

Tall, patrician and with an English wife from a landed family, the 65- year-old “diplomat’s diplomat” confounds most stereotypes of American envoys. Fluent in five languages, including Vietnamese, he has adopted five Honduran children.

These attributes are also reminders of his contentious past. In the 1960s he was a political officer in Vietnam and, as such, would have been familiar with such dirty tricks as the CIA-run Phoenix Program that assassinated thousands of Vietcong. Later he played a part in the peace talks that ended the war.

It was as US ambassador to Honduras during the 1980s that he came under intense scrutiny, accused of turning a blind eye to human rights abuses as the Reagan administration assisted the contra rebels to overthrow the leftist Sandinista regime in neighbouring Nicaragua.

However, his arrival in Baghdad as US ambassador eight months ago proclaimed a new sensitivity to Iraqi concerns, in marked contrast to the high-handedness of Paul Bremer, the departing American proconsul. “Bremer’s style prompted endless criticism, but you never hear anything bad about Negroponte,” said a Washington insider.

Opinions vary on whether he is an ideological warrior, as his critics claim, or simply a meticulous civil servant. By all accounts he is a “can-do diplomat”, but not in the same mould as the neoconservative hawks in the Bush administration. Significantly, his patron in Washington has been Colin Powell, the moderate former secretary of state.

Sir Jeremy Greenstock came to know Negroponte well when their terms as ambassadors to the United Nations overlapped from September 2001 to July 2003. “He was a very good diplomat,” Greenstock said.

“He took the trouble to call on every other member of the United Nations, which is rarely done and was a sign that a great power was prepared to listen. In his time in Baghdad, too, he has been discreet while being firm. He is consultative and open to new ideas.”

Negroponte is married to Diana, an academic and former society hostess whose father was Sir Charles Villiers, chairman of British Steel. But Negroponte’s Anglophilia has its limits, Greenstock implied: “He has no hang-ups about the Anglo connection, as some Americans do. But I’ve learnt never to count on sentiment for England when dealing with senior Americans. You have to earn your access and responses on merit.”

The Negropontes had been married for five years and were based in Honduras when they decided to adopt. Children, the ambassador said in a rare interview, “kept me young”. He also explained why the couple opted to adopt all five from the same country: “These children were all orphans. Life was going to be complicated enough without having siblings from all over the world. Adopting them from the same country ensured they would have a natural bond to each other.”

After serving under seven presidents, Negroponte cited the need to “take care of my kids” when he resigned from the foreign service in 1996.

His mind was changed by his old friend Powell, who persuaded him to leave his lucrative post in the McGraw-Hill media group and fly the flag at the UN. He went one better, raising eyebrows by wearing a stars-and-stripes tie.

He may not mind leaving the razor wire-encircled green zone in Baghdad, where he was barred by State Department rules from taking his family, but the task he faces as director of national intelligence is daunting. At least three prominent figures are reported to have rejected the invitation to manage a $40 billion budget and pull together the work of 15 rival agencies.