It was a superb result for the Wurzels but equally as good for Cardiff as Watford were looking for a sixth win in the last seven League games.
Watford could have gone 2nd, closing the gap on City to 8 points but the 2 - 0 defeat at Ashton Gate was a great result for the Severside teams.
Watford are 4th, 11 points behind City having played a game more.
In the other Championship game tonight Barnsley beat Millwall 2 - 0.