coburn - 9:41 pm on Jan 17, 2005 (gmt 0)

Here's a big clue - our site was ranking reasonably on MSN Beta's first page until we added an H1 tag - boom! Up to #1 for a host of targetted keyword phrases. The rest of the on-page and backlink factors were already in it's favour - this was the final piece of the puzzle.

In response to other conjecture in this post: It's a new domain, has a lot of backlinks, is hosted in the UK, is a large file.