
The poems Frank McLynn referred to, and which Adam Williams made into such an entertaining tale, are actually verses from the Heimskringla. Not only are they set just before the battle was joined at Stamford Bridge, rather than during the actual battle itself, but odds are that Harald never in fact made them up himself (just as well, as I would have suggested he stick to his day job - lopping off heads, amassing booty etc

The verses from the Heimskringla
"It is said that Harald made these verses at this time: --
"Advance! advance!
No helmets glance,
But blue swords play
In our array.
Advance! advance!
No mail-coats glance,
But hearts are here
That ne'er knew fear."
His coat of mail was called Emma; and it was so long that it reached almost to the middle of his leg, and so strong that no weapon ever pierced it. Then said King Harald Sigurdson, "These verses are but ill composed; I must try to make better;" and he composed the following: --
"In battle storm we seek no lee,
With skulking head, and bending knee,
Behind the hollow shield.
With eye and hand we fend the head;
Courage and skill stand in the stead
Of panzer, helm, and shield,
In hild's bloody field."
I did learn something new, though - the word "panzer" originally just meant "armour".