Ok, so this is off topic, which is something I rarely do (ahem), but I'm trying to remember the name of a book series I read back in high school. Here are a few random facts about the book, and some may not be 100% right.

• The book's main character was a British man, and I believe he was from the 1800s.
• While exploring (Africa?) he gets sucked into the Labyrinth. This is a multi-level maze that covers the entire book series.
• It wasn't a maze like a traditional maze, but more like a series of "levels" that were different worlds.
• He meets up with a young woman who becomes his companion. She turns out to be his granddaughter from the future.
• I believe it was 7 books.
• I'm pretty sure an alien race was behind the maze.
• I swear I remember a bi-plane being part of the finale.
• As I said, I read it back in high school, so the publication date would be before 1991.
• On the cover of the last book, I believe there was a picture of the main character, again, looking like what you would expect a 'great white hunter' type person to look like, holding a sword from that time period.

Does this ring a bell with anyone?