Each of these leaders warned his army, when they met, to watch the other,
and not to draw their swords until they saw a drawn sword on the other
side. In that case they were to come on fiercely. So the small party of
chosen men on each side met and drank wine together, and agreed upon a
month's delay before fighting; but while this was going on an adder came
out of a bush and stung a knight on the foot, and he drew his sword to
slay it and thought of nothing farther. At the sight of that sword the two
armies were in motion, trumpets were blown instantly, and the men of each
army thought that the other army had begun the fray. "Alas, this unhappy
day!" cried King Arthur; and, as the old chronicle says, "nothing there
was but rushing and riding, fencing and striking, and many a grim word was
there spoken either to other, and many a deadly stroke."

The following is the oldest account of the battle, translated into quaint
and literal English by Madden from the book called "Layamon's Brut";
"Innumerable folk it came toward the host, riding and on foot, as the rain
down falleth! Arthur marched to Cornwall, with an immense army. Modred
heard that, and advanced against him with innumerable folk,--there were
many fated! Upon the Tambre they came together; the place hight Camelford,
evermore lasted the same word. And at Camelford was assembled sixty
thousand, and more thousands thereto; Modred was their chief. Then
thitherward 'gan ride Arthur the mighty, with innumerable folk,--fated
though it were! Upon the Tambre they encountered together; elevated their
standards; advanced together; drew their long swords; smote on the helms;
fire outsprang; spears splintered; shields 'gan shiver; shafts brake in
pieces. There fought all together innumerable folk! Tambre was in flood
with blood to excess; there might no man in the fight know any warrior,
nor who did worse, nor who better, so was the conflict mingled! For each
slew downright, were he swain, were he knight.