I first met Rajaji, as an M.Sc. student at the Presidency College, Chennai wanting to do a project under him on quantum field theory. I did not know he was such an eminent scientist when I approached him. He agreed to take me when I replied that I knew Dirac did some fundamental work on Magnetic Monopoles, when he asked me if I have heard of it. When he made me work through the 1931 Dirac paper, by asking questions and getting the answers from me, the experience was exhilarating. I joined Prof.PM Mathews as Rajaji was in Japan. Since then, I have had a lot of discussions with Rajaji, both in the work I was doing and also on any paper I was reading through for its own interest. The experience, was very educative, as sometimes, he will stop me and work through the remaining part himself with a different derivation, giving an alternate perspective.
When I was writing the book on quantum field theory, I shared some chapters with him. He said it is going to be one of the good books on this subject and encouraged me strongly to complete it. Advised me to include some sections.
After the book was published, I sent him a copy of it. He went through it in detail, pointing out minor corrections.
I have received emails, out of the blue, expressing his liking of some presentations in it. He readily agreed to write a review as material for the publisher to share publicly.
Though he worked in HEP, he used to attend talks and course lectures in other areas too, when he wanted to learn. He was a complete physicist, with a combination of scholarship and research.
Physics colleagues will miss him as a mentor.