A Bibliopole is a person who buys and sells rare books, particularly rare ones. The BookMine offers a rather more colorful description of the bibliopole as, "someone deranged enough to attempt to sell books for a living."
St. Paul's Churchyard in London was in use as a marketplace as far back as the 14th Century. By the beginning of the 16th Century the churchyard was known as the center of London's book trade. Shakespeare's 1597 first quarto of Richard III includes a statement on the title page indicating that it was sold by Andrew Wise, "dwelling in Paules Church-yard at the signe of the Angell, 1597." St. Paul's remained the center of the London book trade well into the 17th Century. During the Great London Fire of 1666, many of the booksellers attempted to save their stock by placing it in the cathedral's crypts and vaults for safety. Alas, the cathedral, along with the caches of books, was ultimately destroyed in the fire.