Tony Walker at 28 years old in 1985. “I trust Michael [Apted] implicitly,” he says. “He knows the power he holds.”

And then there is Michael Apted, now in his 50th year of following the lives of 14 British men and women, whom he first selected to appear onscreen in 1964 for “7 UP!” when they were each 7 years old. “Give me a child until he is seven,” went the Jesuit maxim favored by the film, “and I will give you the man.” The 7-year-olds are now, astonishingly, 56, and still allowing Apted to peek into their lives every seven years, with the just-released “56 UP,” the eighth installment in the series.