From Hell Ch. 4, page 12

Sir William Gull and his sidekick John Netley are visiting Bunhill Fields, a London graveyard for nonconformist and dissenting christians. William Blake (with whom Gull seems to be pretty obsessed) is resting there, forever in the shadow of Daniel Defoe and his obelisk. Just around the corner is the grave of John Bunyan, who died on August 31 1688, exactly two hundred years before the first Ripper murder.