Watford have done what they needed to, beating Millwall 1-0 to ensure they are heading back to the Premier League.

Three days shy of nine months since their five-season stay in England’s top division came to end at the Emirates Stadium, the Hornets ensured their return to the Championship will last only one campaign with a club record-equalling 18th victory of the season at Vicarage Road.

The manner of the victory would have done little to calm the nerves of those fans denied the opportunity to be inside the ground for another historic day; Ismaila Sarr converting an early penalty to score his 13th goal of the season before the Hornets backed their excellent defensive record to see them over the finishing line.

Watford needed Daniel Bachmann to extend himself on more than one occasion but he was able to keep another clean sheet and shortly before 5pm the celebrations were able to begin.

Xisco Munoz made just the one expected change to the side that performed so well to beat Norwich City on Tuesday night, with Kiko Femenia returning from suspension to replace Craig Cathcart at right-back.

Millwall were thumped 4-1 at home by Bournemouth in their last outing and it was no surprise that Gary Rowett shuffled his pack in response, making three changes and switching to a 3-4-3 formation.

Tom Bradshaw, Mahlon Romeo and Mason Bennett came in for Alex Pearce, Ryan Woods and Kenneth Zohore, who all dropped to the bench.

Although Joao Pedro needed some treatment inside the opening minute following a hefty challenge from Billy Mitchell, the Hornets were soon getting into their passing stride, knocking the ball around confidently.

A chance almost opened up in the fifth minute when, after a good spell of possession, Ken Sema laid a pass inside that Tom Cleverley would have taken in his stride to have a clear shooting opportunity inside the 18-yard box had Pedro not got in his way.

It was the visitors though, who had the first attempt of the contest in the eighth minute when a long throw from Romeo was half-cleared to Scott Malone, who struck an angled half-volley from the right centre side of the area, but Daniel Bachmann claimed it comfortably above his head.

One of Watford’s strengths this season has been their ability to score early and they duly delivered again in the 11th minute to take another step closer to the Premier League.

It came from the reliable right-sided axis of Femenia and Sarr, the latter laying the ball inside to the former who released the Senegalese winger in the area, only for him to be upended by Mitchell.

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Referee Dean Whitestone had no hesitation in pointing to the spot and Sarr confidently did the rest, calmly rolling the ball down the centre of the goal for his 13th goal of the campaign.

The next opportunity came five minutes later when a Cleverley free-kick from the right picked out the unmarked Dan Gosling, but he headed down and the ball bounced up into the arms of the grateful Bartosz Bialkowski.

Will Hughes then fizzed a 25-yard effort wide from a half-cleared corner as the Hornets continued to play with confidence, although they were given a little reminder midway through the half when Bradshaw struck a half-volley wide after Bennett had won a header when the ball was kept alive following a Lions set piece.

Watford had the next chance when a Cleverley free-kick was headed into the danger zone by Francisco Sierralta and Adam Masina tried an acrobatic left-footed effort, which he pulled wide of the target.

The hosts suffered a blow in the 31st minute when Femenia was forced off with what looked like a groin injury, meaning Cathcart came on for another outing at right-back.

Most of the traffic continued to be towards the Millwall goal and the home side were almost in again when Sema was picked out in space in the area, but he couldn’t get his foot around the ball as he tried to apply a first-time finish.

The Lions went close in the 35th minute though, when Jed Wallace laid the ball inside to Mitchell, who connected well with a first-time drive from inside the area which Bachmann had to go full length to his left to keep out.

However, the visitors kept the attack alive and Wallace played the ball back in to Bennett, whose effort on the turn was deflected and clipped the bar as it went over.

The resulting corner was then struck deep to the back of the area where Scott Malone was able to power a free header back across goal, but nobody in orange and white could get on the end of it.

It was a period that served as a warning to the hosts, who had allowed Millwall to grow into the contest more than as the opening period had unfolded although they still went into the break a goal down.

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Millwall carried their positivity into the second half as Danny McNamara did well to find Wallace on the right side of the area and his low centre was hit first time on the turn by Bradshaw, who put it over the top.

The Hornets were still playing within themselves after the restart, which was not helping to ease the nerves of fans watching on from home. And the tension was almost increased in the 59th minute when Bradshaw was allowed to get in behind the defence on the right side of the area and pull the ball back from the byline, but his attempt to pick out Bennett was dealt with by the defence.

Munoz sought to inject some energy on the hour by making a double change, bringing on Andre Gray and Nathaniel Chalobah for Pedro and Gosling.

Within a minute Sarr was appealing for a penalty after being nudged in the back by Romeo as he sought to get on the end of a long pass forward, but the referee was unmoved.

The action soon moved to the other end with Millwall winning two corners, the second of which saw a stretching Bradshaw head towards the far post and Bachmann had to go to ground to claw the ball away.

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It was then Watford’s turn to have a chance when some good one-touch passing ended with Sarr being released in the area, but he chose to try and pick out Gray rather than pull the trigger and Romeo was able to clear.

Rowett made a double change in the 71st minute, bringing on Shaun Williams and Zohore for Mitchell and Bradshaw, and they arrived on the pitch in time to see Gray force Bialkowski into a save with a hooked half-volley after Sierralta had launched a ball forward.

Soon after the Millwall keeper was having to make another stop to deal with a glancing header from Chalobah following a cross from the right.

The Hornets did have the ball in the net for a second time moments later following a delightful one-touch move that ended with Sema applying the finish, but he was flagged offside.

A second Lions double change came in the 77th minute when Hayden Muller and Connor Mahoney came on for McNamara and Malone, and soon after Bennett made way for Tyler Burey.

Carlos Sanchez was brought on for the closing stages in place of Cleverley but it was Millwall who were finishing the stronger, although Bachmann was able to look on in relative comfort as the ball flashed well wide of his goal on more than one occasion.

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After an agonising four minutes of injury time though, referee Whitestone blew the final whistle and with that the celebrations began as the Hornets are again able to look forward to playing Premier League football next season.

Watford: Bachmann; Femenia (Cathcart 31), Troost-Ekong, Sierralta, Masina; Cleverley (Sanchez 84), Hughes, Gosling (Chalobah 60); Sarr, Pedro (Gray 60), Sema. Subs not used: Foster, Zinckernagel, Lazaar, Kabasele, Hungbo.

Millwall: Bialkowski; Romeo, Evans, Cooper; McNamara (Muller 77), Kieftenbeld, Mitchell (Williams 71), Malone (Mahoney 77); Wallace, Bradshaw (Zohore 71), Bennett (Burey 81). Subs not used: Fielding, Pearce, Woods, Bodvarsson.

Bookings: Muller for a foul on Sema (85).

Referee: Dean Whitestone.