He studied law at Bologna, and after his uncle's election he was created successively bishop, cardinal and vice-chancellor of the church, an act of nepotism characteristic of the age.
Gave him a benefice in Parma, and in 1226 he was established at the curia as auditor contradictarum literarum of the pope, a post he held also under Gregory IX., until promoted (1227) to be vice-chancellor of the Roman Church.
Of his numerous works the most notable are: Political Speeches as Vice-Chancellor (Pol.) (in 6 vols., Warsaw, 1791); On the Erection and Fall of the Constitution of May (Pol.) (Leipzig, 1793; Paris, 1868); Correspondence with T.
The vice-chancellor was ex officio a delegate of the press, where he hoped to effect much; and a plan for draining the Thames Valley, which he had now the power of initiating, was one on which his mind had dwelt for many years.
His cousin Giulio, who subsequently became Clement VII., he had made the most influential man in the curia, naming him archbishop of Florence, cardinal and vice-chancellor of the Holy See.
Still was vice-chancellor of his university in1575-1576and again in 1592-1593, and was raised to the bishopric of Bath and Wells in 1593.
On the 30th of April 1689 he moved for leave to bring in a bill to settle the charters and privileges of the university of Cambridge, just as Sir Thomas Clarges did for Oxford at the same time, and he wrote a series of letters to Dr Lovel, the vice-chancellor of the university, on points which affected the interests of the university and its members.
In 1654 Lightfoot had been chosen vice-chancellor of the university of Cambridge, but continued to reside by preference at Munden, in the rectory of which, as well as in the mastership of Catharine Hall, he was confirmed at the Restoration.
He was vice-chancellor of the university in 1628 and 1629, and again in 1638 and 1639.
In 1676 by royal mandate, and was twice (in 1679 and 1695) vice-chancellor of the university.