On a quick trip to Oxford I had the honor of Sir Roger Penrose attending my informal seminar talk on the shadow of black holes and their degeneracies. What a magnificent scientist. His contributions to the understanding of general relativity are only 
matched by very few people in the world and many of the outstanding open problems can be traced back to him. (yes I m a little fan boy 😀 )
Further I had the pleasure of extended discussions with Jan Sbierski on T-orthogonal trapping 
and the gravitational Spin-Hall effect.
