[4] On leaving the chancellorship, he was nominated in May 1406 by Pope Innocent VII as Archbishop of York, but the appointment was vetoed by King Henry IV in the same year.
[citation needed] As bishop, Hallam supported various churches and shrines in his diocese with grants of episcopal indulgences.
On 6 June 1411, Antipope John XXIII (Baldassare Cardinal Cossa) purported to make Hallam a pseudocardinal, but this title was not recognised.
Sigismund, Holy Roman Emperor, through whose influence the council had been assembled, was absent during the whole of 1416 on a diplomatic mission in France and England; but when he returned to Constance in January 1417, as the open ally of the English king, Hallam as Henry V's trusted representative obtained increased importance, and contrived to emphasise English prestige by delivering the address of welcome to Sigismund.
[6] His executors were Masters Richard Hallum, John Fyton, John Hikke, with William Clynt, Thomas Hallum, Thomas Faukys, clerk, & Humfrey Rodeley[8] After Hallam's death the cardinals were able to secure the immediate election of a new pope, Martin V, who was elected on 11 November: it has been said that the abandonment of the reformers by the English was due entirely to Hallam's death;[citation needed] but it is more likely that Henry V, foreseeing the possible need for a change of front, had given Hallam discretionary powers which the bishop's successors used.