Did these two formidable warriors make a pre-agreed pact to co-invade England in the build up to 1066, as some believe? (I don't!)
What possible motive would these notoriously ambitious and avaricious men have had? The embittered and ousted Earl Tostig (Harold's own brother) reputedly visited both men (plus Denmark's King Swein, his cousin) to persuade them to invade.
How could it have even been practical?
The same South-Westerly wind that whisked Hardrada to England in late September 1066 was keeping William pinned to the Normandy coast at exactly the same time?
Surely the military crux of a two-pronged plan is to attack, or at least appear to attack, at exactly the same time?? And of course, there is not even one mention of this in any contemporary source?
King Harald Hardrada of Norway had been locked into bitter internecine warfare with the redoubtable King Swein of Denmark king for 20yrs- and both had designs on invading England (Swein actually prepared a fleet in the late 1040's!)
Why would two deeply avaricious men- each believing themself to be Edward's successor via vague and hollow 'promises' made to both Norway & Denmark in the late 1040's by the Anglo-Norman king- have made vague plans to 'divide and conquer' when we know from original sources that both over-ambitious men wouldn't have shared the glory or wealth?
In short, the two experienced and cunning warriors would never have tolerated, or trusted, each other.