Misc: Which artist went mad after being sent to work as a priest in Belgium?

Questions

Which World Champion heavyweight boxer held the title for the longest?

Which country became the second to issue postage stamps in 1843?

Which author wrote the "Redwall" series of novels?

"All human life is there" - a quotation from Henry James - was used to promote which British Sunday newspaper in the 1950s?

Which Mediterranean island has coasts on three seas - Mediterranean, Ionian, and Tyrrhenian?