A book published in Italy today is set to reignite a smouldering controversy over how close the Nazis came to manufacturing a nuclear device in the closing stages of the second world war. The 88 year-old author, Luigi Romersa, is the last known witness to what he and some historians believe was the experimental detonation of a rudimentary weapon on an island in the Baltic in 1944.

Hitler's nuclear programme has become a subject of intense dispute in recent months, particularly in Germany. An independent historian, Rainer Karlsch, met with a barrage of hostility when he published a study containing evidence that the Nazis had got much further than previously believed.

Mr Romersa, a supporter of Mr Karlsch's thesis, lives today in an elegant flat in the Parioli district of Rome. His study walls are covered with photographs from a career during which he interviewed many of the major figures of the 20th century, from Chiang Kai-shek to Lyndon Johnson. Though he suffers from some ill-health these days, he is still lucid and articulate.

He told the Guardian how, in September 1944, Italy's wartime dictator, Benito Mussolini, had summoned him to the town of Salo to entrust him with a special mission. Mussolini was then leader of the Nazi-installed government of northern Italy and Mr Romersa was a 27 year-old war correspondent for Corriere della Sera.

Mr Romersa said that when Mussolini had met Hitler earlier in the conflict, the Nazi dictator had alluded to Germany's development of weapons capable of reversing the course of the war. "Mussolini said to me: 'I want to know more about these weapons. I asked Hitler but he was unforthcoming'."

Mussolini provided him with letters of introduction to both Josef Goebbels, the Nazi propaganda chief, and Hitler himself. After meeting both men in Germany, he was shown around the Nazis' top-secret weapons plant at Peenemünde and then, on the morning of October 12 1944, taken to what is now the holiday island of Rügen, just off the German coast, where he watched the detonation of what his hosts called a "disintegration bomb".