So, as a diversion for the group, one weekend Dave set up Blackmoor instead of Napoleonics on his ping pong table. The rules we used were based on "Chainmail", which is a set of medieval miniature rules with a fantasy supplement allowing for magic and various beings found in the "Lord of the Rings". I had never played any games like it before, although I had read "Lord of the Rings". Other members of the group had played the game before, but always doing adventures in and around the town of Blackmoor. By the end of the weekend I had fallen in love with the game.(Emphasis mine.)
On this particular weekend, Dave tried a new wrinkle for the game. He had been working all week to prepare a map of tunnels and catacombs under the town and especially under the castle.
So before that first dungeon expedition, people were already playing fantasy adventures, presumably with 1 player = 1 character (or close to it)?
This bears additional digging, including looking up the other people whom Greg Svenson mentions as participants.