His name was Hugo. It was one of those that never really needed a surname. Everybody knew him, it seemed. And everybody called him Hugo. And now, 20 years after his death and after a special service earlier this month in his old synagogue, it still resonates.

For Hugo was a rabbi. A very special rabbi, of whom a colleague once said: "He's probably the most beloved rabbi in Great Britain." To me, he was even more than that. At his funeral, the congregation was counted in thousands - among them the former Archbishop of Canterbury and a sprinkling of cabinet ministers. When my late wife Sara and I went to the shiva, I remember saying to her: "What are all these people doing here? He was my friend."

He was my friend. When Sara came into our bedroom early that day in the summer of 1996 and said one word, "Hugo", I needed to hear nothing more. I knew he had been ill. A few weeks earlier, we met at the home of the Chief Rabbi, Jonathan Sacks. Hugo looked terrible and I cried when I got home.

When the news of his death came on the Today programme I cried again.

We worked together, we went to restaurants with our wives, we visited. But when I think of him, two words inevitably come to mind: Nu, Mich-a-el. A Yiddish word not always used in the Reform community he headed, and then the Hebrew pronunciation of my name. He said it every time we spoke on the phone - and we did that at least once a week.

Usually, he had a joke of the day - not always the sort a rabbi would tell. A master of goodness knows how many languages and dialects, he could use them all. And laugh as he said them, in between a few coughs. He smoked. Too much, as was proved by the need for his grave at the Hoop Lane cemetery.

But, best of all, he used those words to talk Judaism and to give a very personal and instructive reflection on the Holocaust. He was, in so many ways, the survivors' spokesman. He had been in Auschwitz and a handful of less well known camps; each one, seemingly more dreadful than the one before it. I spent a day with him at Auschwitz and another at Thereisenstadt, the way-station to the gas chambers in what had been Czechoslovakia. In the office there, he found an index card bearing his name.

Hugo had been born to a prosperous family in Berehovo in the shade of the Carpathian Mountains in Czechoslovakia in June 1930. His father ran a forestry business, into which he might have gone had Hitler not got Neville Chamberlain to sign the Munich agreement, which gave away his country. His part went to Hungary. As a child of eight, he had witnessed his first act of antisemitism, when in a farm owned by his grandfather, the entire herd of cows had been brutally slaughtered by Hungarian youths.

A few years later, the Germans moved in. Trains arrived and 10-year-old Hugo noticed the label hanging from one of the cattle cars: "We didn't know what it meant, but it said, 'Auschwitz'."

He went back and reported it to the head of the 15,000-strong community (in a town with a total population of 25,000.)

Years later, he told Sue Lawley on Desert Island Discs that the big problem was that the Jews, who were basically living nicely and comfortable in a pretty agricultural town, had virtually no relationship with the rest of the population. "If we had, things might have been better. When it came to it, we had no one to speak for us."

Even before the Nazis came in, with the Hungarians in charge draconian antisemitic laws were introduced. There was a three per cent quota for Jewish children in the top schools. He was clever and one of the three per cent. Then he went to a Jewish school.

"We were incredibly lucky. We had the best teachers in the country, who could only work in a Jewish school. One of them was an Olympic gymnast who gave us lessons in self defence." There was another thing. On Sunday mornings, they had a film show. "We saw newsreels of the gallant Hungarian forces kicking hell out of the Russians, and walking in the background were hundreds of refugees. I recognised some of them as from being from the place next to our home-town. I wrote home about that and they were warned."

In Berehovo, hostages were taken, with the promise of release if the Jews provided a huge gold ransom. "Everyone gave all their valuables, gold rings, plate, everything they possessed and the hostages were released. That was a very clever philosophy. They provided a false sense of security - the Germans, it seemed, could be trusted to keep their word."

Hugo went to the camps with his parents, grandparents and little brother. "As I jumped out of the train, I was met by one of the prisoners. 'Say you're 19,' he told me." Quite a jump from his real age of 13. But he was saved because the guards thought he could be used to work. His younger brother was not so lucky. "He was so small."

Twice, Hugo confronted a Holocaust denier on radio, once on my own programme, once on Radio 4's The Moral Maze. I remember him saying: "Look into my eyes. Tell me I didn't see my little brother walk with my grandparents into the gas chambers. Are you telling me I didn't see that?"

His mother survived and after the war he found her at Berehovo, where she hoped that her husband and son would join her and see the Shabbat candle sticks she had buried and now found in their garden. Only her son arrived. Her husband, Hugo's father, had died of typhoid in the last days of the war.

Of those days, he said: "When people dethrone God and put themselves before God, God cries. He was with us at Auschwitz when I prayed as hard as I knew how."

If there could possibly be a silver lining to the dark clouds of the Holocaust it was that Hugo had got to know a Catholic priest, a fellow prisoner who was once a professor of astronomy. He taught him mathematics by scratching problems on to the stones they were carrying.

After the war, Hugo was one of the "Boys" who came over to Britain. "The Government promised homes for 1,000. They could only find 700". They were boarded in Scotland. In Edinburgh, he learned English for the first time - "a wonderful language" - and at 16 gained a scholarship to study maths at Cambridge. After that, he decided he wanted to be a rabbi and was ordained at Hebrew Union College.

His first pulpit was in Bombay and before long he became first assistant and then senior rabbi at West London. He proved to be one of the finest ambassadors Anglo Jewry had, always speaking as a rabbi, never just as a Reform rabbi.

He was head of the Reform movement, but he spoke as a talmudist. Indeed, in the very first debate between a Reform and an Orthodox rabbi, he was obviously a Talmud chacham, quoting the Rambam and Rashi, and his favourite, Rabbi Nachman of Breslau. On one trip, we went to a tiny synagogue in Bratislava, now the capital of Slovakia. He conducted the service like a Chasid, giving a sermon that was a drosha with all the old intonation.

I remember Lord Jakobovits saying when he himself was at least five years away from retirement: "I wish he was Orthodox. He would have made a wonderful successor."

He always spoke beautifully and made people wish he was their rabbi. West London was the "cathedral" of the Reform movement, with its organ, mixed choir and just one-day festivals. I was a United Synagogue member, yet when I had a problem, he was the one to whom I went. I didn't yet know him well when, in 1979, Sara was taken ill. We were not his congregants and he had not yet met her. That evening, without saying anything to me, he was at her hospital bedside.

Later, she said something that I think summed him up. "You know, Hugo makes me feel clever."

He had that effect on so many. Perhaps because he was always in touch with the world around him, working for interfaith relations, pleading on my show in 1990 for the Muslim majority to rein in the antisemitic fringes who were already spouting antisemitism. "There is a difference between fundamentalism and fanaticism. In a way, I am a fundamentalist Jew. I am not a fanatic." Which is why he was not beyond criticising "some of the ayatollahs in the London Beth Din and among the charedim."

Statements like that endeared him to many. I remember being in his study one day. Looking round the room, I noticed a certificate marking the award of a doctorate. "Hugo," I said, "I didn't know you had a doctorate." Mich-a-el, he replied, "actually, I have three. But I never use them. I'll tell you why. I was at Hebrew Union College in Cincinnati where my first doctorate was awarded. I sat by the phone waiting for it to ring so that I could answer, 'Dr Gryn here'. It did ring and the voice at the other end said, 'Rabbi Friedman here.' Rabbi Friedman had seven doctorates and never mentioned them. I decided at that moment never to use mine."

You never heard him introduced as "Rabbi Dr Gryn" (unlike other members of his family, he always pronounced his surname as 'Green'). Today, he might well have become Lord Gryn. But he wouldn't tell anyone. He was survived by his wife, Jackie, and four children.

Twenty years later, I miss him still.