Dear Sir

Dan Beninson is dead. His recent obituary in this journal lists his activities and achievements and makes it clear that he was a great man. I would like to add some personal words. Dan was my best friend. The friendship began in 1956, when I was called to Rolf Sievert's office to meet a visitor from the secretariat of the new scientific committee of the United Nations, UNSCEAR. I found Sievert involved in a jovial discussion with a person who was very similar to him with regard to outer characteristics - the stoutness and the inevitable big cigar. I was to learn that there was a considerable similarity also with regard to inner characteristics.

Our friendship developed rapidly and noticeably. We found that we had the same views on radiation protection and the basic protection policy, and for that matter on almost everything. We cooperated to the extent that we were somewhat maliciously referred to as the `Beninson-Lindell mafia'. During the forty-seven years of our friendship we never once disagreed on any issue. We reached positions that made it possible for us to influence the international development of radiation protection and the view on radiation risks in ICRP and UNSCEAR. Dan had no ambition to reach such positions; he was brought there by the force of his qualities.

Over the years we met at interesting places around the world and found that social contacts outside the meetings are often more important for the result than what happens during meetings. My admiration and respect for Dan grew for each year. He was the most impressive person I have ever met. He was the true polyhistorian, equally prominent in mathematics and physics as in biology but with far wider interests than natural sciences. He had a great interest in history and in languages. Of course his Spanish, French and English were fluent, but he added quite a number of other languages. He learned Japanese and found pleasure in surprising Japanese children by being able to chat with them. During his last years he seriously studied Chinese. He was a master in chess and had once beaten Bobby Fisher, albeit at the beginning of the latter's career.

Sometimes I thought that I had caught him red-handed when he said something for which I thought he had no real foundation. Usually he explained things so clearly that the audience was misled to think that he dealt with self-evident matters. However, I always found that, on such occasions, I had underestimated him. He had dug deeper than I had believed.

Dan was a polite man, but he had no patience with conceited actions and stupidity. His rage over unfairness could be impressive, the frightening thunder of his powerful voice backed by his ponderous stature. However, he was actually a very kind man. He had a weakness for practical jokes and nonsensical actions that could seem childish. For example, his habit of pressing all buttons when entering an elevator could be quite irritating, but when it really mattered he showed understanding and empathy. And much was forgiven because of his great sense of humour. Wherever he travelled he showed a genuine interest in the activities of the people he met, and his knowledge of names and local habits made people feel that they were visited by a true friend. Which they were. Dan liked to establish friendships.

His wife, Ambretta, a scientist in her own right, was very dear to him. At the occasions when I visited Argentina and met staff members working for Dan, I found them talking about the Beninson couple with respect and deep affection. Ambretta's untimely death in 1983 was a hard blow to him, and after this he took less care of himself, something that greatly worried his many friends.

Dan was not a religious man, his sharp intellect made him inevitably agnostic. However, he had a remarkable knowledge of, and interest in, biblical and theological matters and a curious affection for churches which he always visited with interest, just as he liked to visit museums, both historical and technical. As a true scientist, he made a clear distinction between facts and wishful thinking.

I have been privileged to know and work with most of the great protagonists in radiation protection. In my mind Dan Beninson ranks higher than any of them.