I am sitting in the Central Synagogue in London sipping tea, hoping that I will get a chance to speak to Josef Levinson. Levinson is 93 years old and exhausted after his flight from Vilnius. He has an ongoing high blood pressure problem and has apparently had a bad night. His son Alex, a tall, square-jawed man with a booming voice, tells me that his father has been having doubts about whether to talk to the newspapers.

Levinson is, he says, a modest man who feels uncomfortable in the limelight. He also does not want to cause trouble for the small Jewish community which remains in his native Lithuania. However, Alex reassures me that, as of this morning, Josef has decided to speak.

Levinson has been invited by Barry Marcus, the minister of the Central Synagogue, to be honoured for his work in identifying and building memorials to the 206,000 Jews who died at the hands of the Nazis at more than 200 sites all over Lithuania. The work, which Levinson initiated took nearly four years - another five was spent producing a book recording and photographing the sites of every atrocity.

When Levinson arrives, the strength and single-mindedness with which he carried out his self-appointed task is apparent. Alex translates as his father speaks slowly and clearly in Russian - his pale blue eyes intense as he relates his story.

When the Nazis invaded in 1941 he was in the town of Kalmus. He did not want to hang around for their arrival. He says: "I walked 150 km to the east. The planes were attacking all the time so this was no ordinary walk. The Germans wanted to cause panic among the people so they attacked the road during the day. They were trying to scare people and to stop them moving to the east."

Levinson made it to the Russian border. Those who had escaped were gathered together and sent away on trains. Levinson found himself in a collective farm in the Ural mountains. With characteristic confidence he states that had not previously worked in the agricultural sector but "quickly got the hang of it and was one of the best workers".

After four months, those who could fight were enlisted; Levinson served in the 16th Lithuanian division. He points to a scar on his head. "It is a miracle I am still alive. A shell passed through one side of my helmet and came out of the other side. I wouldn't be here if my head had been a little higher."

He was demobilised and sent to Moscow where, following his recovery, he saw out the war. After the German surrender, Levinson returned to his hometown of Veisiejai in southern Lithuania, where he learned of the massacre of the town's Jews, including his father. "Everybody had been killed. I went to the places where Jews had been rounded up. They had been taken from the surrounding villages and a slaughter organised. The hair stood up on my head as I listened to what happened." At that moment Levinson decided that he had to do something for the memory of those who had been murdered. However he would have to wait 45 years for the opportunity. "I was living in the Soviet Union. The official line was that all those killed in Lithuania were Soviet people. As far as they were concerned, the Jews did not exist."

Nothing happened until the end of 1990 when Lithuania regained its independence. Then the Jewish community, at Levinson's initiative, requested that the Lithuanian government put up memorials. "The government was very supportive," he says. "They issued a formal decree instructing the municipalities to help with the work. But it still took three to four years to identify the sites, to erect the monuments and put everything in order. The places looked awful before."

Despite being well over 70 when the project started, Levinson threw himself into the work. "I would leave on Monday morning to inspect sites and to supervise the work and not come back until Friday." He also spent years researching the archives. "I read the stories of what had happened. I spent years going through the documents of court cases, of the Lithuanians and Germans who were searching for Jews to kill. There were some terrifying stories. I cried as I read about them."

But surely a man of his age would tire at that kind of intense work? I ask the question through Alex, who bursts into laughter at his father's reply. "My father says he was young and full of energy."

The work of creating memorials finished in 1993. Then, Levinson set to work for another four years on a book which would comprehensively catalogue and provide photographs of every site.

At first, in the flush of independence, the Lithuanians were helpful. However, Levinson acknowledges that there is still a huge amount of antisemitism in the country. "During the war there were people who risked their lives to save Jews. But there were others who helped the Nazis. They didn't disappear. These people started a campaign saying that the Jews collaborated with the Communists to send people to Siberia. They tried to justify the killings by saying that the Jews were killing Lithuanians or at least sending the Lithuanians away to die."

However, the Lithuanian government did appreciate what he had done. They gave him a diploma in recognition of his work. It was an immense effort but Levinson feels it was worthwhile. To have achieved his goal gave him what he describes as "a spiritual satisfaction".

He adds: "I don't know what these memorials look like now. My guess is that some may have disappeared. If the municipalities don't look after them they will deteriorate. But at least people will know what happened, not for ever but at least for hundreds of years to come.