Watford passed another test in their quest to achieve promotion back to the Premier League at the first attempt in strong fashion with a 3-0 victory over Birmingham City.

Goals from Ken Sema, Nathaniel Chalobah and Andre Gray ensured the Hornets secured a fifth successive victory for the first time this season, made it nine wins in their last ten outings and picked up three points for the 15th time at Vicarage Road in the current campaign to move them six points clear in second place at the time of writing.

Xisco Munoz’s men have made a habit of starting fast this season and they did it again in just the fourth minute when Sema applied the finish after Neil Etheridge had saved a Joao Pedro shot.

The hosts had opportunities to double their lead before the break, but they also had to do their share of defending as Birmingham showed their quality, particularly from set pieces – one block from Chalobah a particular highlight.

Watford needed the cushion of a second goal and it was Chalobah who delivered it, rising to thump home a far-post header following a good delivery from a Dan Gosling corner.

The third arrived when, moments after their introduction from the bench, Jeremy Ngakia won the ball back with his first touch, sent Andre Gray scampering clear with his second and his fellow replacement did the rest.

Munoz was forced into two changes from the side that eased to an emphatic 4-1 triumph at Rotherham United.

The absence of Ismaila Sarr after being forced off on Tuesday night had, to an extent, been expected, but that was compounded by the loss of the player who would have been expected to move from midfield to replace him on the right, Philip Zinckernagel, with a hip problem.

Gosling came into midfield and, to the surprise of some, Isaac Success got the nod to start up front and begin a league game for the first two in two years. Pedro moved out to the right of the forward three in Sarr’s absence.

Fresh from a much-needed 2-1 victory over Reading in midweek, new Birmingham boss Lee Bowyer was able to name the same starting XI for his first away match at the helm.

Bowyer would have been hoping his side would start positively but within four minutes they were to be behind.

Pedro played the ball into Success on the edge of the penalty area, he held it up before returning it to the Brazilian who drove forward into the left side of the box before hitting a left-footed shot which Etheridge did well to save diving to his right. However, he could only parry the ball out and Sema was following in to score his second goal of the week and make it 1-0.

The Hornets did have to deal with a couple of deliveries into their box thereafter, but were happy to play very much in second gear for the next ten minutes or so having made the early breakthrough. And that lead should have been doubled in the 17th minute.

Sema was the supplier with a corner from the right that was allowed to run right across the six-yard box to Adam Masina who stabbed the ball narrowly wide of Etheridge’s right-hand post.

The Blues’ keeper was less concerned by a scuffed Success shot on the turn soon after, but after a stoppage in play following an injury to Lukas Jutkiewicz the visitors could well have equalised had it not been for a superb block from Chalobah.

Birmingham had already shown they could be a threat from set-pieces and it was from one such situation that the ball was kept alive in the Hornets area by Harlee Dean and it dropped to Jeremie Bela, only to the Watford captain fling himself in front to block his shot on the edge of the six-yard box.

The hosts had gone off the boil for a spell but just after the half-hour they had two opportunities in quick succession.

First Chalobah’s ball was turned on first time by Gosling to Pedro on the right and he teased Kristian Pedersen before playing in a low cross that could not pick out a yellow-shirted teammate. The Hornets kept the ball alive though, and soon after Pedro clipped in a cross which Gosling met with a looping header that drifted over the top.

Watford were also appealing loudly for a penalty for handball before Pedersen picked up the game’s first booking for hauling down Pedro on the edge of the box after the Brazilian had turned him inside out.

Success was then in on goal after latching onto a Sema pass inside but Dean just got enough of the ball as the Nigerian went to pull the trigger.

Birmingham continued to ask questions though, and four minutes before the end of normal time at the end of the first half Maxime Colin took a ball in his stride as he cut in off the right and advanced into the area, but Masina made a well-timed challenge. The Blues’ right-back was able to keep the ball alive and picked out Scott Hogan, whose effort was blocked behind by Kiko Femenia, but the flag was raised for offside.

The card count was levelled up at the end of the first half when Success, frustrated at a decision not going in his favour, needlessly fouled Rekeem Harper and saw yellow as a result.

Birmingham started the second period on the front foot as they continued to seek to get back on terms, but it was their opponents who had the first good opening.

Sema sent Success scampering in behind but his first touch was too heavy and that gave Etheridge the opportunity to come off his line and make a blocking challenge to save. Watford again kept the ball alive though, recycling to Chalobah to hit a right-footed drive from the edge of the box that was deflected later. Moments later, the lead was to be doubled.

Gosling took a good, deep corner from the right and Chalobah did really well to lose his marker, get free beyond the far post and measure a header back across goal and into the net to give the Hornets daylight.

That assist was to be Gosling’s last involvement as he made way for Carlos Sanchez soon after, with Joseph Hungbo also coming on for Success.

Bowyer responded with a triple change on the hour, with Hogan, Alen Halilovic and Bela making way for Jonathan Leko, Ivan Sanchez and Mikel San Jose.

The hosts were forced into a further change midway through the second half, when Masina’s good afternoon was prematurely ended by injury and Achraf Lazaar came on in his place.

Despite being two down, the Blues still kept trying to get back into the game and Jutkiewicz hit a powerful effort not too far wide with 15 minutes to go.

Dean then headed a Colin cross over the top before Munoz followed Bowyer in making a double change – and it couldn’t have worked out any better.

Ngakia won the ball back with his first touch and with his second sent Gray racing away. The striker had time to think about what he was going to do as he raced clear and the answer was emphatic as he calmly dispatched the ball beyond Etheridge to make it 3-0.

Daniel Bachmann, who was able to celebrate another clean sheet, wasn’t unduly troubled by a San Jose shot before Watford twice could have added a late fourth.

First Hungbo chose to go it alone, instead of laying a chance on a plate for Gray, and was denied by Etheridge, before the young winger did square inside for his fellow replacement and again the Birmingham keeper came out on top.

It mattered little though, as the home side were able to celebrate another job well done that opened up a six-point cushion ahead of Swansea City’s late kick-off with Cardiff City and left them in a strong position heading into their enforced break from action.

Watford: Bachmann; Femenia, Troost-Ekong, Sierralta, Masina (Lazaar 67); Chalobah, Hughes, Gosling (C Sanchez 56); Pedro (Ngakia 79), Success (Hungbo 56), Sema (Gray 79). Subs not used: Foster, Wilmot, Cathcart, Perica.

Birmingham City: Etheridge; Colin, Roberts, Dean, Pedersen; Halilovic (I Sanchez 61), Gardner (Sunjic 78), Harper, Bela (San Jose 61); Jutkiewicz (Cosgrove 78), Hogan (Leko 61). Subs not used: Prieto, Friend, McGree, Seddon.

Bookings: Pedersen for a foul on Pedro (35); Success for a foul on Harper (44).

Referee: Darren Bond.