Previous chapters have shown that the medieval Italian inquisition was not a solo performance by the inquisitor but a team effort, heavily reliant both on its lay and clerical staff and on the main mendicant orders, with which it was much more closely integrated than is often supposed. We now take a step back to evaluate the overall relationship between the inquisitor and his major institutional partners, the commune and the diocesan bishop, as it developed over the century following Ad extirpanda. The bull created a three-cornered framework within which the partnership (and its inevitable tensions) might be managed. How robust did this prove in practice? Where – and why – did adjustments occur? In pursuing heresy, did the inquisitor become primus inter pares, as is often suggested, or was the situation more nuanced?

Although the inquisition quickly entrenched itself as a bureaucratic institution over this period, acquiring physical property, establishing staff and routines, and accumulating new powers and privileges, in Italy it did not fully succeed in dominating its lay and clerical partners. This was partly because inquisitors, small in number, needed both their aid and their authority, and partly because of the robustness of civic structures and the potential for commune and bishop to make common cause against an over-mighty inquisitor. Indeed, in some cases civil authorities became less acquiescent and more aggressive in asserting their rights as time passed. An important factor was that the inquisition's replacement activities after extirpating the Cathar heresy had little public resonance and could lead both to serious clashes and loss of moral authority. Such weaknesses (and their own financial interest) made bishops and civic authorities unwilling to cede their roles in relation to heresy, though they did not necessarily exert them all the time.

The most obvious factor affecting the inquisition's relations with cities and bishops was the current state of local politics. This was not a straightforward binary choice between Guelf and Ghibelline. The equation of Ghibelline sympathies with heresy, except through a tendency to be branded rebels, is an old canard rebutted by a number of scholars, including recently Baietto and Lomastro Tognato. In her detailed work on Vicenza, Lomastro Tognato shows that even arch-Ghibellines such as Ezzelino III da Romano occasionally persecuted Cathars.