The reference is to Cardinal Adrian of Castello, or Corneto, Bishop of Hereford, and of Bath and Wells. Alleged to have been involved in a conspiracy against the Pope he moved to Venice. After the Pope’s death he sailed from Venice but was never seen again, and was said to have been murdered. This seems precisely the kind of story in which Venetian tourists and Venetian guides delighted.
[Version 0.05: May 2008]