Given that Muggles back then tended to burn witches and wizards at the stake, Slytherin's concern is not misplaced.

Fortunately, times change--a pity that the basilisk remained.

Ooh! I've got chills! Especially after reading the conversation between Slytherin and his Serpent at the very end. The only thing I'd like to point out is your use of the word "loo"; it sounded a little out-of-place in a 900AD story? But I thought the idea that the centaurs didn't like Slytherin was an interesting one - particularly since your character seems to have a very disdainful view of other magical creatures (like the house-elves). I wonder what exactly he did? My favourite bit though, was when the Basilisk hatched and swallowed the toad "in one bite". Fantastic image.

What an excellent idea! I love stories that have that spark of originality to them, especially when they are well written as this.