Who is Beauchamp Millward Comber from Flash for Freedom! and what is their importance?

Comber serves as the Third Mate on the ship Balliol College under Captain Spring. He advocates for better treatment of the slaves aboard ship. Before his death, Comber confesses to Flashy that he is, in fact, acting as a spy for the Royal Navy and collecting evidence on Spring. He makes sure Flashy has the sealed documents before his passing.