Phylum: Ochrophyta   Family: Acinetosporaceae

Hincksia secunda (Kützing) P.C. Silva, 1987

A filamentous seaweed no more than 20 mm long. Grows on other algae, especially kelp. Rarely recorded but almost certainly under-recorded

References: 
Newton (1931) - A Handbook of the British Seaweeds