19th November, 2016
Etienne Capoue volleyed the Hornets into the lead – their fastest Premier League goal – before Roberto Pereyra curled in a second after 12 minutes.
Leicester pulled one back when Riyad Mahrez converted a penalty after Miguel Britos’ clumsy foul on Jamie Vardy.
But the Foxes could not score again and remain without an away league victory this season.
Leicester become only the third reigning top-flight champions, after Leeds in 1992 and Blackburn in 1995, to start a Premier League season without a win from their opening six away games.
Watford had been embarrassed 6-1 at Liverpool in their last match and boss Walter Mazzarri demanded an improved performance.
But even he could not have expected the blistering start they made as they went ahead in the opening minute.
Leicester midfielder Danny Drinkwater, who had missed England’s matches against Scotland and Spain with a rib injury, gave the ball away and that enabled Pereyra to sprint down the left wing before his cross was flicked on by Troy Deeney, with Capoue volleying past Ron-Robert Zieler.
Pereyra doubled the advantage shortly after, cutting inside Drinkwater on the edge of the penalty area and curling the ball into the corner.
Leicester fought back with a penalty after only 14 minutes, but were frustrated and denied by a resolute home defence as the hosts held on for the win.