In 1940, aged eight, Michael Henderson was sent to live with a family in the United States. He set off in his black and green school cap, with his National Insurance number on a chain round his neck. “I called out the latest grown-up phrase I had picked up: ‘See you after the duration,’” he remembers. But the duration turned out to be longer than he expected. After five years in Massachusetts he returned home to a mother he did not recognise, and a country that seemed battered and small. About 10,000 British children were evacuated to North America during the war, often leaving as children and coming back as strapping, well-fed teenagers. Their experiences were varied, but many had a happy time, and have maintained lifelong transatlantic ties.

Michael Henderson, who was evacuated with his younger brother, Gerald, was one of the lucky ones. The boys left their Surrey prep school to live with the delightful-sounding Hinchman family, near Boston, and spent the war enjoying a New England childhood of summer camps, frosty Christmases and relaxed, co-educational schools. Now Henderson, a journalist, has written a book about the evacuation, partly to capture evacuees’ memories before they are lost, but also to honour the unstinting generosity with which thousands of Americans opened their homes to unknown children. “With the way things are now, and America not always being as well thought of as it was, I wanted people to have a greater awareness of what they did. It can’t have been easy for them. We weren’t ideal children, after all.”

Most were from middle-class homes, with evacuations arranged privately through friends of friends. One link was between Yale and Oxford academics.

The politicians Jeremy Thorpe and Shirley Williams were both evacuees, as was the poet Anthony Thwaite. Henderson discovered that one train taking children to their port of embarkation contained a future Cabinet minister, a judge, a lord mayor, a knight, and assorted dons and doctors.

One evacuee found himself in Hollywood, being taught to swim by a future president, Ronald Reagan; another, in Princeton, New Jersey, received help with her homework from Albert Einstein. However, it was the little things that struck these junior exiles so forcefully: hamburgers and Popsicles, lights blazing without black-out restrictions, and a school vocabulary that turned break into recess, and prep into assignments.

Faith Coghill, now Faith Garson, a retired nurse, arrived in Boston aged 12 with her own brother Egerton and the Henderson boys (the group is pictured on the cover of Henderson’s book, above). She believed the host families were “keen to make us little Americans so the American children would like us better. They cut my plaits off and took away my shoes with straps, but it was all well intentioned.”

School was a revelation. English accents and Scottish kilts caused some children embarrassment, while, in New York, children in short trousers were asked, “Where’s the other half of yer pants?” Many found the work easy, because they had started school a year earlier than their American contemporaries, and some felt contemptuous of the American system. But more settled happily into a routine and enjoyed the absence of uniforms and beatings, and the easier relationships with teachers.

Like many of the evacuees, Faith Coghill found coming back harder than going, and remembers the misery of returning to a rule-bound Oxford high school and the disparaging attitudes of teachers there. “One said to me, ‘Do you mean you don’t know the subjunctive?’ and I said, ‘No, I don’t know anything.’ She didn’t like me answering back, either.”

However, she feels the experience shaped her life in a positive way. “One has a much more global attitude. You’re much less insular. And although you might be critical of the States, you see the good as well.”

The evacuation was not popular in all quarters. The royal family thought it would look bad if they sent their children away, while Churchill considered the programme poor for morale. In the end, it was a tragedy that stopped the exodus: 77 children drowned in September 1940 when their ship, The City of Benares, was torpedoed. A group of 54 boys and girls from the Actors’

Orphanage, a home and drama school in Chertsey, was one of the last groups out. They thought they were going to Hollywood, where the orphanage president, No l Coward, was allegedly making arrangements, but were instead taken to an institution in New York, although they did get visits from their Hollywood sponsors, including Charlie Chaplin, Cary Grant and Douglas Fairbanks. One of the group, Granville Bantock, who later became an engineer, says: “It was a terrific experience, although going to school in the Bronx was a huge shock to the system, and my education was totally messed up as a result. When I came back I was so far behind that I didn’t get into grammar school.”

Penny Moon, then Penny Jaques, also had her life changed by the experience.

Aged only three, she was packed off to live with a relative in Canada. When she returned four years later (running along the station platform, she says, shouting, “Ain’t I cute?”) it was to bitter sibling hostility and tearful struggles to learn pounds, shillings and pence. The trauma eventually led her into a career as a psychotherapist, and an unbending conviction “that children do better with their parents even if the circumstances are dire”.

But these were “very difficult times”, Michael Henderson points out, and his book vividly evokes a lost world of patriotism and stoicism. The historian Sir Martin Gilbert, who was himself evacuated to Canada, writes in the foreword: “It is a true history of a traumatic period, and there were several occasions when in spite of myself I found tears in my eyes.”

One, he says, was when he was reading the words of “There’ll Always be an England”, a song he had sung heartily, aged three, on his voyage out.

See you after the Duration: the story of British evacuees to North America in World War II by Michael Henderson is published by Publish Britannica Pounds 13.95 (www.publishbritannica.co.uk).The Children’s War exhibition at the Imperial War Museum, London, which opens on March 18, includes material on WW2 evacuation to the US and the Commonwealth. Schools bookings on 020 7416 53135444, www.iwm.org.uk