Oscar Garcia has stepped down as Watford boss following his recent health scare and has been replaced by Billy McKinlay
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Callum Harriott's first league goals of the season secured Charlton's Sky Bet Championship survival with a game to spare as they sank Watford 3-1.
The rookie winger opened the scoring in the first half and then put the seal on a dramatic win with a superb late strike.
There were plenty of nerves around The Valley when Troy Deeney equalised for Watford in the second half, but Charlton captain Johnnie Jackson fired them back into the lead before Harriott's clincher killed off the Hornets.
Former Spain international Albert Riera has joined Championship side Watford until the end of the season.
The ex-Liverpool and Manchester City winger has agreed the deal following his release by Galatasaray in January.
OFFICIAL: #watfordfc defender Lucas Neill has signed for Doncaster Rovers on a one month loan deal
Watford have been fined £5000 by the Football Association after admitting a charge of misconduct.
The Hornets were accused of failing to ensure their players conducted themselves in an orderly fashion and/or refrained from provocative behaviour against Ipswich on December 21.