Who is Sam Quatt from The Stars My Destination and what is their importance?

Sam Quatt is an old compatriot of Jisbella McQueen. He is retired, but he comes out of retirement to help Jisbella. Sam is captured after sustaining a head wound during the raid on Baker's facilities. He then tells Jisbella and Foyle to leave him behind, after which, the pair steal his space yacht to retrieve the treasure from the Nomad.