Workplace Family Tree Discovery

I work as a civil servant. A couple of years ago I joined a new department and bumped into another chap (Tim) who shares my surname. We chatted for a while and it came out that we are both interested in family history and had started compiling our respective trees. His family was from south west Devon and mine from north west Devon. Its took a few months searching and travelling around before it became apparent that we have an ancestor in common who was born in NW Devon in 1710. We are 7th cousins; not once, twice or thrice removed, just exact 7th cousins. The two lines diverged in the 1760s and as far as we are aware had no contact until Tim and I bumped into each other. Genetic testing has confirmed the link on the paternal line. What are the odds that two people start at the same department at the same time with the same surname and are exactly related?