The strange disappearance of Martin Luther King's rabbi

She was disappointed, too, by "the absence of the religious and moral sense of the march". Heschel doesn't blame Selma's "very talented" director, Ava DuVernay, entirely, but suggests that she's conforming to a current tendency in cinema "to avoid conveying, in film, the power of religiosity". However, "Dr King was a very religious person," she says, "and the Civil Rights Movement was a religious movement."

It was partly religion that had helped to create an immediate bond between King and her father when they met at a conference on religion and race in Chicago in 1963. Both men, says Heschel, were "imbued with the Bible" and used similar language. While Abraham was "very moved" by the way that King had made "Exodus and the prophets key to the Civil Rights Movements". This, Heschel believes, explains why so many Jews became involved. "If he had made the Gospels central, I don't think as many Jews would have been drawn to the movement," she suggests.

In fact, according to one historian, a disproportionate number of white civil rights activists were Jewish. Whereas many had felt ashamed of being Jewish in the 1950s, "The movement," says Herschel, "gave Jews an opportunity to express themselves as Jews, if they wanted to. It felt like a Jewish movement . . . But we know, of course, what it's like to suffer, to be disenfranchised. We know from Jewish experience."

Abraham himself had escaped Poland in 1939, and reached New York, as a refugee, in 1940. However, his mother, three sisters and many relatives weren't so lucky. "The whole world that he grew up in [disappeared]," says Heschel. "Nobody in his family survived, unless they got out before the war." As an activist, he drew parallels between the antisemitism that he experienced as a child in Poland, and witnessed as an adult in Germany, and racism in the United States, and often compared poverty in America to the poverty of his Polish childhood.

When he met King, it gave him a chance to work on a national level, says Heschel. They became friends, and when Abraham received a telegram asking him to join the march in Selma, there was no question that he would go. Heschel admits that she feared for his safety, as the first attempt to march had become known as 'Bloody Sunday', after state troopers and local police dispersed the non-violent protesters using tear gas, clubs, and, according to DuVernay's film, even whips, hospitalising over 50 people.

"My father received the telegram on a Friday and it was a very nervous Shabbat," says Heschel. "After Shabbat was over, and we made Havdalah, my father left. I went outside and he kissed me goodbye and then got into the taxi. And I remember it vividly because I didn't know if he would come back. But he had made it clear that this was the most important thing a person could be doing at this moment. So I was proud of him. And I was relieved when he came home."

Later, one of King's most trusted lieutenants, Andrew Young, told Heschel that everybody in the Civil Rights Movement had had a copy of Abraham's book about the prophets "in their hip pocket, and had read it when they were in prison. I thought that was great."

In 1968, her father invited King and his family to their Passover Seder, but he was assassinated just before. Today, she recalls the profound impact he made on her life. Listening to his speeches, he, like her father, had brought the Bible alive for her in a way that Hebrew school hadn't. "It made me feel that the Bible was about today. Our day and age. That it was about overcoming the problems of our time, conquering them, softening hardened hearts. That the prophets had a power that was extraordinary. Every time I heard him I was in tears. And I always felt I was in the presence of a really extraordinary religious person."

This, she feels, is where DuVernay's film falls down. Heschel understands from interviews that the film-maker wanted to "humanise Dr King", and therein, for her, lies the problem. "I know there's a lot of that going around," she says, "but humanise means, sometimes, to trivialise or to make things banal." To her, seeing King "fussing over his neck-tie and feeling uncomfortable wearing this fancy suit for the Nobel Prize" in the film's opening scene, isn't interesting.

"What's really interesting about Dr King," she says, "is that he was a great human being. It is, in fact, his greatness that I am interested in. Not that he's just like me or everybody else in the world."

Perhaps touching on a consequence of the democratising effects of the internet and social media, Heschel says DuVerany is not alone in doing this. "I think it's a general tendency in our society to avoid greatness and turn extraordinary human beings who changed the world into one of many people. Of course, there were lots of people who were involved in the Civil Rights Movement who haven't gotten their due. But there was still something great."

As racial anxieties increase in the United States and antisemitism rises in Europe, his message of inclusiveness is as valid today as it was in 1965. Instead of erecting barriers between faiths, creeds and races, "Dr King said, 'Let's come together, all of us'," says Heschel. "Then you had someone like my father, who said, 'Yes, antisemitism and racism, both. It's not one versus the other.'"

At least, it shouldn't be. After writing an article about Selma, Heschel says she started receiving emails from people saying that Jews should stick to worrying about antisemitism.

"Now my father didn't feel that way. And I think it's too bad," she says. "I think we shouldn't just focus on our own issues for our community but open the door, and that's what Dr King did for us."