Books in the Purple Band series

The Stone Age is very cold and Pod needs something to warm his bottom He realises he needs a good pair of underpants but puzzles over what to make them from. Stone is too heavy, wood is too splintery, and mud is too yucky... Nothing seems to work In the end, a baby woolly mammoth gives Pod the inspiration he needs and he knits himself some very warm woollen underpants. Bring on the Wool Age