NAOMI: People think my dad is quite scary. But he’s a poppet. He just enjoys being seen as a stern Victorian patriarch. It’s a bit of a pose. He can name more of the songs of Marie Lloyd, the sensation of the 1890s, than he can of the Beatles.

We share migraines. His grandmother had them and he passed them on to me. My first real memory is of having a blinding headache on holiday. Dad has migraines of different colours. I once asked him: “What colour is your migraine?” He said: “Blue and green.” My mother, who paints, and doesn’t have migraines, didn’t know what we were talking about. We also share a silly, sometimes macabre sense of humour.

People presume that an Orthodox-Jewish home is an emotionally rigid environment. From sunset on Friday to sunset on Saturday, we observe a strict sabbath, when we don’t use money or anything electrical, or travel by motorised transport. We also obey the kosher food laws: only certain animals are kosher, and they must be slaughtered in the correct manner. And we don’t eat milk products and meat products in the same meal. It’s a restrictive way of life, but it does bring some rewards.

I had a lot of freedom, though. Our house was filled with books. I had a television in my bedroom. But my dad didn’t know how to relate to children. He had been born in the middle of the second world war. Grandma’s brother was shot down over Germany, and her remaining brother died tragically after the war. Then she lost her parents. So he grew up in a house where people were constantly dying. I think he felt he had to not tread on people’s emotions.

If I’m sad, he has nothing to offer me. But if I’m angry, he’ll say: “We need to do something about this.” When my brother, Eliot, joined the Cubs, his badge book had scientist and explorer badges, which weren’t in my Brownie book. I had cookery and home-maker badges. At nine years old I knew to be cross. Dad said: “We shall write a letter to The Times.”

It was published and taken up by the Fawcett Society, who invited me for tea. Two years later the Brownies’ badges were changed. My father gave me the confidence to believe that you don’t have to put up with things. It’s had a huge influence on my life. I once disagreed with what he’d written in The Jewish Chronicle and I wrote to them. My letter was published. He was so pleased.

As a teenager I would compare him unfavourably with friends’ fathers, who were sympathetic if they cried over boyfriends or fell out with classmates.

My dad could name more of Disraeli’s friends than he could mine. We had huge arguments. But he treated me as if I had the capacity to be his intellectual equal.

No ground was given to the fact that I was six years old. If I asked about the causes of the first world war, I would be told. At eight, he took me round Oxford. In Lincoln College he announced: “This is my old college, Naomi. One day you’ll come here.” And I did. I wanted to study English but he talked me out of it. So I did PPE [philosophy, politics and economics], which I didn’t enjoy. Socially I had a brilliant time. At school it was hard to find people who understood me; at Oxford I found a whole bunch of other Jews who understood completely.

I moved to New York while my father was working there. It’s where I forged an adult relationship with him and let go of the frustration I’d had with him as a child.

I’ve never had an unproblematic relationship with Orthodox Judaism. I test it out to probe the weak spots and often feel quite angry. It’s a bit like a parent. There are things about it I love and things I really detest, but I can’t help having a relationship with it.

Having been brought up both Orthodox and intellectually independent, it’s not clear who my parents expect me to marry. They’ve never pressured me. But Dad wants grandchildren — with or without a husband. If Eliot produced children, that would be very helpful! But he’s busy doing other things. We both completed academic degrees to please Dad. Now we’re pursuing more creative things.

My novel is set in the Orthodox Jewish community of Hendon, where I live. It’s caused some controversy — it includes a lesbian relationship, although I think it’s as much about faith as about sexuality. I didn’t show the book to my parents until I’d sold it. Naively, I thought The Jewish Chronicle would give me a kind review, but it was the worst newspaper review of all. Dad said: “It was always going to happen. The Jewish community doesn’t know how to take what you’ve written.”

My mother is a very religious person. For her, Judaism is about the eternal. My father’s Judaism has more of a respect for the human side. I’ve been overawed by his ability to pursue justice without fear. I’m proud of the many things he’s done in a quiet way to help people.

I’m also proud that he keeps on saying things nobody else in the community will say. He was once interviewed by The Jewish Chronicle. This quote made me realise who he is: “I’m all for washing dirty linen in private, if it could be done, but the most important thing about dirty linen is that it should be washed.” Brilliant!

GEOFFREY: I don’t apologise for being a Victorian father. I was hard but kind. I don’t think Naomi was frightened of me — she had respect and affection. She wrote me an e-mail recently to say: “Thank you and Mummy. Growing up in this house was an education in itself.”

Orthodox Judaism is not just a religion: it’s a way of life involving every aspect of one’s conduct, from the most public to the most personal, a framework in which to live one’s life in this world, not in any other. It is demanding, but also beautiful and strangely liberating. Ultimately it’s a way to communicate with my maker.

Naomi and I look alike. And we’re both unconventional. It’s unusual to be unconventional and religious — we glory in it. Naomi loved books. When she was a teenager we had ferocious arguments about writers, particularly Virginia Woolf. I dissuaded her from studying English and I’m not sure she’s ever forgiven me.

I had an arranged marriage. Every Saturday I sat on the sofa at the rabbi’s house. The girl of the week would be invited to meet me. Naomi has made it quite clear I’d be wasting whatever time the Almighty has allotted to me if I even think about an arranged marriage for her.

When she moved to New York we became friends. Every Thursday we met for dinner at a different kosher restaurant and it was the highlight of my week. But I began to realise that, exciting as my split existence was, I wanted to be back in the UK. Then Naomi confided to me that she wanted to give up her job and apply for the creative-writing course at UEA. I could never have taken that leap. After she sold Disobedience, she sent me the typescript. I couldn’t put it down. It explores how seemingly contradictory forms of love can be accommodated in an Orthodox framework. It is the story of the triumph of love over bigotry. I phoned to say: “Naomi, you’ve written a brilliant book. In my humble opinion it will be praised in the non-Jewish world and damned in the Jewish world.” By and large, Geoffrey’s prophecy has come true. One person even told me it was pornographic and disgraceful. But it’s neither. It’s a work of fiction, written without malice. Naomi has told the truth.

When she won the Orange prize, Marion and I were ecstatic. I’m proud of Naomi for having the courage of her convictions to write. The Talmud says: “If I am not for myself, who is for me?” She has remained true to her religious beliefs and her upbringing.

People think of Orthodox Judaism as a monolithic creed. It isn’t. It’s a broad church. I’m an unashamed unconventional Orthodox Jew, often adopting viewpoints mainstream which Orthodox Jews find uncomfortable, but which are positioned squarely within the Halachah, the rabbinically ordained framework of Orthodox Judaism. My daughter is a living example, as I hope all my family are, that you can be an Orthodox Jew and live in this world.

Disobedience (Viking) is out in paperback on April 1

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