Festooned over it all are heaps of straw-coloured strands, floppy like long catkins or cereal bran sticks. I scoop up a handful and marvel at the intricate beauty laid out in my palm. These are the tubes of the sand mason worm, Lanice conchilega, normally buried like the razor clams but washed ashore by rough seas instead. Each multicoloured tube is a necklace of tiny fragments of shell and rock, cemented together to protect the body of the worm, in a similar technique to that of caddis fly larvae in rivers. The worm has a fringed top of tentacles, a miniature palm tree, for catching any passing food of plankton, algae or decaying plants; it’s normally the only thing visible when it sticks out of the seabed.