For many of us, December 2 was a sad day. That morning, Prof. Daniel Catovsky passed away in London. He was born in Buenos Aires (Argentina) and went to London in 1967, with his wife Julia Polak, for a short training period. They never returned and stayed in London for the rest of their brilliant career and life. Daniel worked first at the MRC Leukaemia Unit, Royal Postgraduate Medical School, Hammersmith Hospital and then at the Royal Marsden Hospital. He was, in many ways, a giant. He deserves to be remembered for his major contributions in the characterization of acute and chronic leukemias, but also for his endless role in the training of innumerous fellows and for the kindness and availability he always showed, despite the many drawbacks witnessed in his difficult life.

Workwise, he was one of the first to utilize, already in the seventies, the laboratory tools available those days to refine the characterization of lymphoid malignancies: from morphology, to immunophenotype, to cytogenetics and even to electron microscopy. How many today remember the sheep and mouse rosettes, and the Tμ and Tγ T-cell subsets? Daniel was, undoubtedly, a forerunner of what is now known as translational research. Those were the times of the FAB (French–American–British) classification, when the FAB group met at the MRC Leukaemia Unit of the Hammersmith Hospital several times. His intense work allowed to better characterize and classify chronic lymphocytic leukemia (CLL), hairy cell leukemia (HCL), the rare HCL variant, B- and T-cell prolymphocytic leukemia, adult T-cell leukemia/lymphoma, splenic lymphoma with villous lymphocytes, and to open the way to investigating previously unknown defects of the non-neoplastic host immune system in CLL and HCL. From his group also came the first description of the so-called atypical CLL. These were all major contributions in the field of chronic lymphoproliferative disorders, with which everyone became familiar years later through the WHO classification. He also played a key role in the design of innovative therapeutic strategies for all these conditions. The refinement in the classification and management of chronic lymphoid leukemias owes him a lot.

Coupled to the above has been the endless number of fellows from all over the world who trained with him from the seventies onwards. Many of them have then covered prominent positions in their countries of origin. The main reason to go to work in Daniel’s laboratory was certainly the optimal use he made of the more modern technologies applied to answer relevant clinical questions, but also his open and interactive attitude, his generosity, availability, and disposition to other people. This is something the younger generations do not often encounter. Many working with him learned how to analyze data and how to write a paper. He used to go over the draft of a paper in the evening or over the weekend. And it was always a very thorough correction… often leading to quite a different paper! Time was never wasted, he was generous with advice, recommendations, suggestions, and ideas. Many of the old fellows and registrars have remained over time in close contact with Daniel, often maintaining productive collaborations.

Two of us (RF and JVM, Figs. 1 and 2) were lucky enough to spend several life-changing years at the MRC Leukaemia Unit, Hammersmith Hospital between the late seventies and mid-eighties under Daniel’s supervision. This allowed both of us to discover a new world of applied clinical research, to learn the importance of teamwork and collaborations, and to have the opportunity to meet, in person, practically the entire world of hematology that passed through the Hammersmith Hospital, starting with the members of the FAB consortium. The Hammersmith in those years was one of the leading hospitals and its Grand Round on the Wednesday morning was famous worldwide. This also applied to the Hematology Department directed by Prof. Sir John V. Dacie and, later, by Prof. Lucio Luzzatto, and in particular to the MRC Leukaemia Unit headed by Prof. David A.G. Galton, where the two senior staff members were Daniel Catovsky and John M. Goldman. A group of absolute top players in leukemia, very British with one clear touch of Latin exuberance!

Fig. 1
figure 1

DC and RF.

Fig. 2
figure 2

DC and JVM.

Daniel has succeeded in a long-lasting professional life of great relevance and impact, with multiple recognitions, always maintaining a rare simplicity, kindness, and availability. All in the face of an undoubtedly difficult life. In 1976 he lost his brother Hector, one of the many “desaparecidos”, victims of the military junta in Argentina that lasted 7 years. His eldest daughter, Marina (Mina), a barrister, died prematurely at the age of 47, after being hit by a motorcycle while crossing London Bridge, in 2011. His wife, Julia (Dame Julia Polak), for many years one of the most cited female scientists in the world, had to undergo a heart-lung transplant in 1975 from Sir Magdi Yacoub for pulmonary hypertension. At the time of her death, in 2014, she was the longest surviving heart-lung transplant.

Daniel leaves in very many of us (Fig. 3) strong and fond memories, which will remain much cherished - something that doesn’t always happen…

Fig. 3
figure 3

DC with KRR and many other colleagues/friends and earlier fellows.