`He was courteous but very silent. He was good with children. His eyesight may have been impaired, but he had an ear open to the world." This is how Alex Leon recalls James Joyce, who, between 1928 and 1939 was an almost daily visitor to his family's flat on the rue Casimir-Perier in Paris. Joyce came to consult with Alex's father, Paul Leon, who acted as the writer's unpaid secretary and adviser: "In writing Finnegans Wake, Joyce was breaking the bonds of language. He would check ways of saying things with my father, who could speak seven languages." The two often sat at a round table, Joyce gravitating towards his favourite chair.

This chair - a small, comfortable armchair with mahogany arms - has been re-upholstered since then, but is otherwise unchanged. It now rests, along with that table and three other chairs, in the James Joyce Centre on North Great George's Street in Dublin. The furniture makes up the centrepiece of a new exhibition, opening today, in what will now be known as the Paul Leon Exhibition Room.

Bob Joyce and Ken Monaghan, descendants of the great man himself and chief executive and cultural director of the centre respectively, are very pleased with the acquisition (made with the help of the Heritage Council).

"Try it, you might feel the inspiration," says Joyce, pointing to the chair. I oblige, enjoying the cosy feel of the chair, which is of dimensions one would normally associate with a woman rather than the rangy figure of Joyce. This privilege - sitting for a moment where the great man had ingenious cogitations - is not one that will be extended to members of the public. Joyce stresses: "The furniture will be roped off."

There was some initial thought of purchasing the flat from Alex Leon to set up a museum in Paris, but funds were short, so the furniture was purchased instead. Leon, who lives in England, is relieved it is now in reverent hands: "The apartment is being rented and I felt the condition of the furniture would only deteriorate if I left it there." The intention of the Joyce Centre is to replicate the room in Leon's apartment as it appeared when Joyce paid his daily visits.

Paul and Lucie Leon moved into the apartment in 1925, shortly before Alex was born. "The last time my father met Joyce there would have been in 1939, and since then there have been so many upheavals - it is a miracle that so much has stayed intact."

As Alex begins to reminisce about earlier times, he slips into referring to Joyce as he must have done when he was a child: "Mr Joyce would come over almost every day, except at weekends. My father didn't accept payment. He wanted to be independent. I remember him explaining, with a laugh, `so if I can't take anymore I can stop'."

Joyce was notoriously difficult with his friends, taking umbrage and breaking off relations at the drop of a hat, but it is a mark of the close and trusting relationship he had with Leon that their only falling-out was one brief blip in an otherwise harmonious friendship: "Artists, especially one of Joyce's calibre, are inevitably centred on their art, sometimes at the expense of the niceties of social intercourse," Leon explains.

Although Alex Leon is doubtful that any of the writing of Finnegans Wake actually took place around his father's table, a translation into French of the Anna Livia Plurabelle section was completed there during the winter of 1930/1, with the aid of a third party, the French poet Philippe Soupault.

Soupault, on seeing Leon and Joyce walking along the street, quipped: "There goes the lame leading the blind." Alex Leon explains: "My father was very stooped from poring over books." But the scholarly Leon was not without a sense of humour: "I remember my father, joking with Joyce, threatening to sell that table if Joyce carved his name on it."

Paul Leon was a Russian Jew, a lawyer, philosopher and sociologist who had published two books. His wife Lucie was a fashion writer with the New York Herald Tribune: "She was the bread-winner. It was very unconventional for that time," says Leon. Neither of them had any realistic sense of the danger their lives were in as the second World War began and Nazi anti-Semitism swept Europe. James and Nora Joyce were frail and in poor health, unhappy about moving to a village near Vichy where they were eventually joined by the Leons. In spite of the risk involved, the Leons returned to Paris, and while they were there Paul had two concerns. The first was to rescue as many of Joyce's papers and belongings as possible from his abandoned flat. The second was to be there for Alex, then 16, as he sat his baccalaureat.

"I remember my father going to Joyce's flat, with my mother and uncle, in spite of the curfew. He put Joyce's papers into 19 brown manila envelopes and brought them to the Irish Embassy, with the proviso that they should not be opened for 50 years [the papers were exhibited at the National Library in 1992], to protect people still living," says Leon. "A number of Joyce's things were being put up for auction, because he had not paid rent for some time, and my father, mother and uncle went to the auction and bought back as much as they could. My father felt this was a duty and you would do it for a friend.

"My parents didn't realise what shape this thing was going to take. My mother wanted to continue with her journalism and my father wanted to be close to his 4,000 books. In 1941 [after Joyce's death in Zurich earlier that year] my father bumped into Samuel Beckett on the street in Paris one day and Beckett asked him: `What are you doing here?' My father told him: `My son is going through the baccelaureat tomorrow and I want to be there'. He pinned a lot of hopes on my education."

The following day, August 21st 1941, Paul Leon was arrested with "about 50 other prominent Jewish people and sent to an internment camp in Drancy," Alex Leon recalls. There, Leon became ill with oedema because of the bad food. "My mother, a very heroic person, joined the Red Cross and took charge of distributing packages within the camp. She managed to see my father secretly several times." In December Leon was transferred to the Compiegne Camp, which turned out to be a staging area for onward transport, and in 1942 he was sent to Auschwitz. Less than a fortnight after his arrival there, he was dead. (In late 1941, the Irish government declined Giorgio Joyce's request to intervene on Leon's behalf).

"My mother and I saw him for the last time in Compiegne just before he was due to get on the train. It was like something out of Dante's Inferno, all those ghostly men. He had to be supported by two people, he was so ill. My mother broke through the German military police cordon and gave him food, but she was pushed back almost immediately. Then we went to the other side of the station and waved through an opening in the fence. Then we couldn't see him any more because one of the cattle trucks came up."

It wasn't until the end of the war that Lucie met a survivor of the 1,700 on her husband's shipment, who told her that Leon had been shot only 10 days after she and Alex had seen him on the railway platform: "They were building Birkenau, an extension of Auschwitz, and during the march to that site, he fell behind and was shot because he couldn't keep up."

Alex and his mother managed to get to Monaco and he has spent his working life as a businessman, for many years with Pepsi Cola, and latterly in healthcare products. He will be in the James Joyce Centre today, for the unveiling of the Paul Leon Exhibition Room, where his father's loyalty, modesty and erudition are commemorated.

The exhibition of furnishings from Paul Leon's home is open from today at the James Joyce Centre, North Great George's Street, Dublin 1.