Where should we put it? In 1992, the artist Gunter Demnig embarked on an extraordinary project. Small cubes with a brass plate would be placed outside the homes of Holocaust victims. These Stolpersteine — stumbling stones on the pavement — would mark the location of the place where the victim last freely chose to live. It is both thrilling and moving, a fine example of how creative art can achieve great eloquence.

There are thousands all over Europe. And now one would be installed for my grandmother, Margarete Wiener-Saulmann. She had died of the hunger and disease that Belsen had inflicted upon her. But where should we put her stumbling stone?

Grete and my grandfather Alfred had not wanted to leave Berlin and become refugees. But my grandfather’s work as an anti-Nazi activist, archivist and Jewish community leader made remaining in Germany impossible once Hitler came to power.

So should the Stolpersteine be in Berlin?

Alfred and Grete had created a family home in Amsterdam, at 16 Jan Van Eijckstraat. My mother had been born in Berlin but she came to the Netherlands as a baby and has no memory of it. In Amsterdam, the family enjoyed freedom and the children experienced happiness until the Nazi invasion.

It was in the Netherlands that Grete and the children were arrested and their experiences — transportation to Westerbork, suffering in Belsen — became part of the Dutch Holocaust. So the Stolpersteine should be in Holland.

Yet even this didn’t settle the matter. For the family had not been arrested in Jan Van Eijckstraat. In the summer of 1941, Grete had been forced to move and took the family 20 minutes to the south-east to live in an apartment at 25 Westerscheldeplein. The reason for this move was simple: She had run out of money.

Alfred had taken his work to London in 1938 and the invasion of the Nazis had cut him off from his family, together with any resources he had. So there had been no choice but to move somewhere cheaper.

It was at Westerscheldeplein on 20 June, 1943 that the family had been arrested. There is a case that it is outside this apartment, on the pavement where they had waited to be taken away, that the Stolpersteine should be set. Yet our view — my brother, my sister and I — is that while the family had lived in freedom at 16 Jan Van Eijckstraat, they had never lived in freedom after that. In May 1940, their true freedom had ended.

But we were influenced by one other thing. The family home in Jan Van Eijckstraat had also been the place where my grandfather, with Grete’s assistance, had worked. Along with his colleagues, he had created the greatest archive of material on the Nazis. The Jewish Central Information Office, as it was named, had been housed in number 14, accessible from the domestic quarters.

The archive eventually became known as Wiener Holocaust Library, now based in London’s Russell Square.  On 1 February this year, it celebrates its 90th anniversary. So, along with the Stolpersteine, there will be a plaque placed on the Jan Van Eijckstraat building. It seemed right that the Stolpersteine should be in the same place. And that there should be stones for other colleagues who worked at the office and were killed by the Germans.

On Monday 29 January, with my family present, Gunter Demnig installed the Stolpersteine and speeches were made, including one by the particularly excellent and lovely Dutch ambassador Karel van Oosterom, who had made the whole thing happen. It was a wonderful occasion.

But even thinking about the location had been stimulating, forcing us to think about the meaning of being free and the definition of the word “voluntary”.

There is a dispute going on about the right sort of Holocaust memorial for Britain. I am a partisan in this dispute, believing strongly in the design and location of the proposed memorial. But I have great respect for those who disagree and for their arguments.

And this is not the place to rehearse our disagreement. Instead, I want to say something we can all agree upon, as I don’t think Grete would want us to argue. I just want to attest to the value of physical memorial and the role of creative design in marking historical events.

The power of Gunter Demnig’s work is intense. To our family, his little stumbling stone is priceless.