Who is Spook. from Last Exit to Brooklyn and what is their importance?

Spook appears in the short story, and Baby Make it Three. He wants nothing more from life than a motorbike. He is so obsessed that he wanders everywhere wearing a motorbike helmut and spends most of his time admiring the brand new bikes in motor bike shops. Finally, through saving his every penny, he manages to afford and do up and old police bike.