Heidar Helguson continued to write his second chapter in Watford folklore after his brace sank Scunthorpe.
The striker is already a Hornets legend after scoring 64 goals in five successful years at Vicarage Road before moving to Fulham in 2006.
And the 32-year-old took his tally to five goals in only his second start since returning to Hertfordshire on loan from QPR with trademark headers in two first-half minutes.
Strike partner Danny Graham bagged the third to extinguish any hopes of a Scunthorpe comeback three minutes into the second half as Malky Mackay's side secured their third successive home win.
Former Norwich defender Mackay had to sell his best players to balance the books after taking over in the summer, but he has built a decent side around shrewd loan signings Tom Cleverley and Henri Lansbury and they could be dark horses for the play-offs.
The visitors, by contrast, look like struggling this term and were never in the game after Helguson opened the scoring in the 18th minute.
Cleverley, who this week extended his loan spell from Manchester United until the end of the season, swung in a cross which Helguson nodded past Iron goalkeeper Josh Lillis.
And the celebrations had barely died down when Helguson struck again, Graham's cross this time met by the Icelander who nipped between the centre-halves and thumped another header into the net.
With Scunthorpe reeling, Adrian Mariappa had a shot cleared off the line and Helguson drove straight at Lillis.
As the interval approached Helguson squandered the chance to complete a first-half treble when his header drifted the wrong side of the post and full-back Lloyd Doyley dragged a shot wide.
But Watford did not have to wait long for the third and it went to Graham, who ended a seven-game drought with his seventh of the season.
The former Middlesbrough forward latched onto a clever pass from Arsenal loanee Lansbury and coolly slid the ball past Lillis.
The hosts could have had more, with Lillis stepping in to deny Graham after Helguson attempted to tee up his fellow frontman.
Helguson also shot straight at Lillis before leaving the field to a standing ovation to be replaced by Nathan Ellington 15 minutes from the end.
Ellington should have got on the scoresheet in injury time after a strong run into the box but he blazed his shot over.
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