Dang! Where does this book fit? The DWTL places it in 1973, and I adjusted that one year and put it in- but if Wuffles is already an elderly dog, it doesn't work. Moreover, as Old Dickens pointed out, the War of the Sourceror presumably occurred during the Lancre Timeslip, else the Witches would have noticed it. If Wuffles was born in 1973, as indicated in The Truth, then "elderly" would be a minimum of ten years (actually, terriers are long-lived dogs and generally don't become "elderly" until 12-13 or older). That would mean that Sourcery would have to be placed in 1983-84, just before the end of the Timeslip, and that Ezrolith Churn was the next Archchancellor after Coin and the one preceding Ridcully.
On the other hand, that same passage in Sourcery- the one wherein Vetinari first appears - contains some uncanonical statements, such as the claim tha the merchant families had ruled the city for "twenty centuries."
Moving Sourcery down roughly a decade does happen to address the question of Vetinari's ascent to the Patricianship at what had appeared to be a troublingly early age. Solicitr 14:40, 22 April 2010 (UTC)