At the end of my first day, on Thursday, I went to a string theory seminar on gravitino dark matter, which only accelerated the onset of 4pm jetlag crash. On Friday Eugenia Cheng was down from Sheffield to speak about an inductive definition of weak $n$-categories using terminal coalgebras. This is very interesting since it involves both the category Set and the category Top of topological spaces; the latter in order to supply an operad for the construction. Everybody in the group went to the seminar lunch.
Later in the afternoon, there was a seminar entitled Example of a 2-category at the Mathematical Institute, but most non mathematicians were forewarned by the word Langlands in the abstract, and indeed one of the questions at the end was: er, so what does this have to do with categories?
The mornings are still very chilly, but the weather has been quite pleasant so far, and the 20 minute walk to work passes some spectacular historical buildings.