Sonoyta was able to find confirmation, on that Oxford Union appearance, in the form of a blog entry. Click below for the full writeup.
The most amusing question of the afternoon? An American dude, with ?If you could high-five anyone in the history of the world, who would it be?? Utterly stumped, Portman asked him who his choice would be. Quick as lightning, he replied ?you?, and duly got his wish, to the amusement of all.