Convivium

It is the Degree-conferment ceremony at Unseen University, in which the Archchancellor, University Council, eighth level wizards, masters and doctors proceed from the University to the Opera House. They are led by the Commander of the Watch, or if there isn't one, then by a man carrying a pot of mustard and a quill. Foreign dignitaries, city officials and nobles are also invited to this ceremony, and upon arrival at the Opera House, the Patrician will present the graduates with their degrees. This was a plot-point in Jingo.