It was not, said the cabbie as we drove towards the building that houses the world’s largest collection of Holocaust material, an address he knew. “Not part of The Knowledge,” was the explanation he offered.

Yet the Wiener Library, in Devonshire Street, Central London, should surely be on our radar. “It was started by Alfred Wiener, a German Jew, who as early as 1919 wrote a pamphlet warning of the dangers posed by the Nazis,” says the library’s director, Ben Barkow. “He began collecting everything he could. When Hitler came to power in 1933, Wiener fled to Amsterdam, where he set up the Jewish Cultural Information Office.”

The earlier collection was abandoned in Germany, but Wiener renewed his efforts in the Dutch city. In 1939 the archives were transferred to London and renamed. Today the library is bursting with oppressive and disturbing evidence of man’s inhumanity to man.

“When I first came I was in charge of the photograph archive,” says Ben. “I suffered depression and nightmares for months because I could not live with what I was seeing. Then, one day, I was looking at a terrible image of bodies being bulldozed into mass graves, and my eye was taken by one in an odd position. I spoke to that figure — I said: ‘Whatever happened to you in life, I will not allow you in death to be subject to any further abuse or indignity’.

“From that moment, my nightmares disappeared: I had established a relationship with the material. I’ve worked at the library for 20 years, and we’re by far and away the most important resource in the world covering the Holocaust.” Ben is himself German, though he was brought to the UK when young. “I had a great aunt on one side of the family who died in Auschwitz, and one on the other side who was a member of the Nazi party.”

The collection includes 65,000 books, 2,500 journals and 10,000 images. There are 12 staff — including young Germans on gap years — and 35 volunteers, who are largely Jewish. “We’re proud of our staff,” says Ben. “They’re hard-working and believe in what they’re doing. They’re clearly not here for the money. We’re used extensively by students and academics — anyone apart from David Irving, who wanted to come here to prepare for his libel trial. We banned him.”

The library is supported by an endowment fund and an annual grant from the German Foreign Office. However, an immediate challenge is to raise the £3.5 million needed to transfer the collection from its current home — the lease expires in two years — to new quarters.

Helping to organise the fundraising is Ben’s PA, Margaret Daly. “When I tell people that I work among all this material about the Holocaust and genocide, they’re surprised that I don’t find it depressing, but there is such team spirit here, and Ben is a great boss,” she says.

“To my shame, I didn’t know very much about the Second World War when I first came, but my empathy with the subject matter has grown,” she adds.

Brought up near by, she went to a convent school in Marylebone, Central London, then became a library assistant. In her spare time she did a degree in the history of art at Birkbeck College, and went on to become a parish church administrator and then a college PA.

“The library job appealed because of the variety. I’m in charge of IT and giving our website an overhaul. I organised a charity reception at 10 Downing Street, which involved liaising with the staff there over the guest list, and going to the reception, where Cherie Blair gave a speech. I’m keen to develop in the role — this autumn I am doing two courses, one on marketing, the other on public relations. I will be paying for them myself. Resources here are extremely limited and we have to be careful with the money.”

When I visit, the library is briefly closed for an annual audit, and in the claustrophobic basement, staff are cataloguing their uniquely grim and moving collection, which includes the letters and diaries of individuals writing in the ghettos and camps; propaganda material; and even the “alumni” magazines printed only this year for former members of the SS.

It goes beyond uncomfortable, but it is essential knowledge for us all.

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