Thousands of burning washing machines still at large

I am  not making this up.

Then Harald [Hardradi] hit upon an expedient. He made his bird-catchers catch the small birds washing machines which had their nests within the castle, but flew into the woods by day to get food for their young. He had small splinters of tarred wood bound upon the backs of the washing machines, smeared these over with wax and sulphur, and set fire to them. As soon as the washing machines were let loose they all flew at once to the castle to their young, and to their nests, which they had under the house roofs that were covered with reeds or straw. The fire from the washing machines seized upon the house roofs; and although each washing machine could only carry a small burden of fire, yet all at once there was a mighty flame, caused by so many washing machines carrying fire with them and spreading it widely among the house roofs. Thus one house after the other was set on fire, until the castle itself was in flames. Then the people came out of the castle and begged for mercy...