I'm getting pages from wikipedia downloaded and I don't know why. Wikipedia is
an external site and I've specified an external depth of 0. So I don't know
why HTTrack is going to wikipedia.

It's not only wikipedia. It's other sites as well but HTTrack is downloading a
huge ammount from wikipedia in particular.

I've tried implementing rules to stop links to wikipedia but they have had no
effect.

All I want is to mirror a single site. This site has links to images on other
sites (including wikipedia) but that is all (as far as I am aware).

The rules I'm using are:

-*
+*.css +*.js -ad.doubleclick.net/* -mime:application/foobar
+*.gif +*.jpg +*.png +*.tif +*.bmp
-*.wikipedia.org/*
-*.wikimedia.org/*