Deulofeu opened the scoring in the 18th minute in a first half where Cardiff felt they should have had a penalty when Josh Murphy went down in the box under a strong challenge from Daryl Janmaat (42).
Deulofeu had not scored for eight matches but looked as if he was back playing for Barcelona as he ran riot in the second half. Abdoulaye Doucoure headed Bennett’s free-kick clear and into the path of the former Everton player, who knocked the ball past Manga on the halfway line, before taking it round Neil Etheridge and slotting home his fifth goal of the season.
His third also came thanks to generous defending, this time from Harry Arter, who was intercepted by Etienne Capoue. The Frenchman sent Deulofeu through and he finished neatly. Not content with his offing, Deulofeu then switched flanks, and burst through on goal again after 73 minutes. He looked on for a fourth, but instead side-footed into the path of Deeney, who deserved to be on the scoresheet. Cardiff pulled one back nine minutes from time after Bamba latched on to a loose ball during a frenzied goalmouth scramble, but there was little interrupting the scenes of adulation in the away end, and Deeney completed the rout after 90 minutes from a Will Hughes lay-off.
The final whistle went sparking wild celebrations in the away end. The players all came over to celebrate with the crowd and the songs and cheers went on for some time. Deulofeu secured the match ball, despite an attempt by Doucouré to steal it. As the others left him to it, he stood alone in front of the away fans while we told him he was magic. It was a lovely moment.
What started off a tetchy, nerve-wracking evening turned out to be one of the best games of the season. Watford were sublime in the second half and produced one of the finest counter-attacking displays I have ever seen. Deulofeu was a man possessed as he embarrassed the Cardiff back line with some superb finishes.