Watford ended a three-match losing run with the comfortable dispatch of West Ham in David Moyes' first game in the dugout for the visitors.
David Moyes' reign as West Ham manager began in disappointing fashion as the Hammers were beaten 2-0 at Watford to remain in the Premier League's bottom three.
The Scot was chosen as Slaven Bilic's successor during the international break, but defeat in his 500th game as a Premier League boss was as painful as the 26 he suffered with relegated Sunderland last term as missed chances at one end were punished by the goals of Will Hughes and Richarlison at the other.