Watford bounced back to the Premier League at the first time of asking after Saturday's 1-0 win over Millwall sealed promotion.
Brentford's win at Bournemouth earlier in the day meant that only three points would be good enough for Xisco Munoz's men to be promoted alongside Norwich, who came down with them last season.
Ismaila Sarr's early penalty gave Watford the perfect start, but they had to withstand a nervy finale to guarantee their place back in the prestige and riches of the English top-flight.
Prior to Munoz's appointment on December 20, automatic promotion looked unlikely after dip in form under Vladimir Ivic.
However, 17 wins in just 24 games under the Spaniard helped amass a 10-point lead over Brentford, who have just three games left to play.
The Bees are now at least guaranteed a playoff spot with Bournemouth, Barnsley and Swansea almost certain to join them in the battle for the final promotion place.
Barnsley moved nine points clear of seventh-placed Reading with a hard-fought 1-0 win over struggling Rotherham thanks to Carlton Morris's early goal.
A week after securing their promotion, Norwich closed in on the Championship title with a 3-1 win at Queens Park Rangers to maintain their five-point lead over Watford with two games to go.
Xavi Quintilla, Max Aarons and Emiliano Buendia were on target for Daniel Farke's men at Loftus Road.
At the other end of the table, all of the bottom three lost to give Wayne Rooney's Derby a reprieve despite the Rams losing 2-1 at home to Birmingham.
Rotherham and Sheffield Wednesday, who lost 3-1 at Middlesbrough, are still four points behind Derby, although Rotherham have two games in hand to try and overturn that gap.
Bottom-of-the table Wycombe were realistically relegated by a 2-1 defeat at Cardiff.
The Wanderers are six points adrift of Derby but have also have a 13-goal gap to bridge on goal difference.
