Did the pope (then surrounded by Norman warlords in Italy/Sicilily) ever actually issued a Papal flag to William at all? Or did he merely extend a nominal, verbal promise of support which was "pounced upon" by propagandists such as the hagiographer, William of Poitiers)?
Papal banners were only ever issued during this era to endorse wars against muslims (then in Spain and Siciliy/S.Italy) or against those who had rebelled against Papal authority (Harold had not)- and not against fellow Christians.
A papal legate to England in 1062 found NO corruption worth noting- even against Archbishop Stigand- whom William left in office until 1070 (along with other English clerics)!
Odd for a man who had vowed to invade England to alledgedly to rid the land of supposed ecclesiastical corruption and pluralism?
In 1080 there followed a Papal decree which set the penance for having killed in a 'public war', a war that was sanctioned under the terms of the Truce of God.
It was after King William's coronation on 25th Dec 1066 (by Archbishop Ealdred, who also crowned his friend, King Harold!) that problems arose from promises the Pope claimed William had made and that King William denied (1080).
The disputes were:-
* On the amount of Peter's Pence owed to Rome,
* the right of Rome to call upon Norman Bishops to attend Rome with a
full complement of milites.
In fact Bishop Odo was arrested for perhaps attempting to obey such a summons, by William, when accompanied by his own knights!
While the question as to if William promised to make England a Papal fief continued to be denied throughout William's life.
Is it coincidence that Archdeacon Hildebrand's plans never succeeded, as William's possible support through Norman adventurers failed to appear?
When Harold broke his supposed 'oath' to support Duke William's claim to the English throne, it fell on two members of the church to find a solution from which the Church would most benefit.
* Prior Lanfranc of the Abbey of Bec, a trusted servant to Duke William, who was entrusted to go yet again to Rome to gain papal support for William.
* While in Rome, Archdeacon Hildebrand (future pope Gregory VII), the political power behind the papal throne, had his own plans far beyond assisting the Norman Duke.
It is probable that these two formidable ecclesiastical politicians had met on Lanfranc's earlier mission to Rome to obtain papal sanction and blessing on the controversial marriage of Duke William and Matilda- delayed due to accusations of consanguinity. (The pair founded two abbeys to allay such grief - Abbey aux Hommes and Abbey aux Dames)
This mission was successful and we can assume that two such similar clergymen established a strong and useful partnership.
Archdeacon Hildebrand's plan was to establish a temporal power base throughout Italy and beyond, by using those newly seized lands established by Norman mercenaries, such as Robert Guiscard Conqueror of Naples.
Some of these new nobles had sworn themselves as fiefs to Holy Mother Church, thus these 'Priest-Knights' obtained political recognition through the Church.
By increasing the number of devoted Normans willing to conquer new lands for the church and establish new fiefs, Rome could obtain a massive power base not only in Italy but over the alps and indeed wherever such fiefs could be founded.
The Archdeacons only problem was the lack of Normans capable of seizing such lands. And William was holding out?
It would further these plans greatly if the Duke of Normandy and perhaps the future King of England would give his political support, if not his available knights?