An interesting consideration is just when Lord Vetinari became Patrician. Clearly this isn’t him (Vetinari eating crystallised jellyfish? —I don’t think so. Besides, Interesting Times makes it quite clear that Vetinari does not know who Rincewind is).
However, Terry has always denied this interpretation:
"I’m pretty certain that the same Patrician was in all the books. […] He’s clearly lost weight and got more austere. It must be the pressure. As for racehorses and so on—Vetinari is not the first Patrician, and no doubt the earlier ones, like Lord Snapcase, were often crazed, greedy and acquisitive. So he has inherited all sorts of things. But he doesn’t change anything without a reason."
When the people on afp were not immediately prepared to take his word for this (after all, what does he know—he’s only the author…), Terry conceded:
"How about: maybe he was Vetinari, but written by a more stupid writer?"
Which was grudgingly accepted. Still, discussion about the differences between the “early” and the “recent” Patrician continues to flare up regularly. When some people on alt.fan.pratchett questioned whether Vetinari would really be the type of man to throw the kind of party described in Mort, Terry answered:
"I’ve always thought the Patrician is a party animal. Can you imagine waking up next day and remembering all those witty things you said and did, and then realising that he was listening?"