I first came across Sharpe on TV in spring 1995, when it was during its third year, and loved it. This was before Amazon and DVD box sets, and tracking down the episodes I'd missed was an adventure that ran for many weeks. I read all the books, rationing them to one a week, and was wildly enthused for months.
Then, in autumn 1995, I stumbled across The X-Files, which was just starting its second season on British TV. Within weeks, I was utterly obsessed. At the start of 1996, we got a computer with internet acccess. The first thing I did was look for X-Files Usenet groups. Within minutes, I'd discovered this thing called fanfic. Within weeks, I was writing it.
Obsession was nothing new for me. When I was 8, I was utterly obsessed with Swallows and Amazons. I made what I would now think of as fanart, and did what would now be called cosplay. I persuaded my parents to take me to the Lake District, where I visited the places the books were set, and did the sort of things the characters did.
At 9, I was similarly obsessed with The Lord of the Rings. At 10, it was The Three Musketeers and its sequels. At 11, it was The Scarlet Pimpernel. At 13, it was original series Star Trek. At 14, it was The Lord of the Rings again, far more hugely than before. In every case, I made up stories about the characters in my head, and made art. In every case, it was entirely solitary. It never crossed my mind that other people might feel the way I did, and that it would be possible to meet them. Going to university was a revelation, since for the first time in my life, I was able to meet people just like me.
So, in a way, I have many fandom might-have-beens, in that everything I've listed above could have led me to years of obsession, interaction, and fanfic-writing, had the internet existed back then. But Sharpe always strikes me as my greatest fandom might-have-been, since, for me, it missed the Internet Age by just a few months. Had we bought a computer just a few months earlier, Sharpe might have been my First Online Fandom, rather than The X-Files.