Spurs huffed and puffed at Wembley but lacked inspiration without injured England pair Harry Kane and Dele Alli and looked to be heading for their third Premier League defeat in five games after Craig Cathcart's first-half goal.

But Son, back in the side after South Korea were knocked out of the Asian Cup, equalised with 10 minutes to go and Spanish striker Llorente grabbed the winner in the 87th minute.

Watford took the lead when Northern Ireland defender Cathcart headed home from a corner whipped in from the left in the 38th minute, with goalkeeper Hugo Lloris caught in no-man's land.

Spurs had enjoyed the lion's share of possession in the first half without creating much of note and Watford threatened on a number of occasions when they ventured forward, with Gerard Deulofeu looking lively.

Spurs boss Mauricio Pochettino was relieved to be able to recall Son and he was the main threat in the early stages, looking to run at the Watford defence at every opportunity.

Son went close with a left-footed strike from outside the box in the ninth minute and six minutes later Christian Eriksen's deflected shot forced Watford goalkeeper Ben Foster into a scrambling save.

But Watford nearly took the lead shortly before the half-hour, when Deulofeu put the ball narrowly wide of Lloris's right-hand post and they eventually broke the deadlock through Cathcart.
Spurs poured forward immediately and Son flashed a ball across the open goal but there was nobody to apply the finishing touch.

Pochettino thew on Lucas Moura for the second half to add to his side's firepower and the home side mounted an all-out assault on the Watford goal.

Spurs went agonisingly close to an equaliser in the 51st minute when Llorente somehow contrived to skew the ball over the bar from two yards out after Foster could only parry the ball into his path.

They continued to pour forward throughout the second half, with Llorente missing another golden chance, but could not find a way through a resolute Watford defence.

But finally the pressure told as Son drove home following a Llorente assist, which infused the side with fresh belief.

As time ticked away, Llorente headed home a Danny Rose cross and Watford were unable to respond.

Defeats against Chelsea in the League Cup semi-finals and Crystal Palace in the FA Cup fourth round in the past week have left Tottenham boss Pochettino contemplating another trophy-less season.

Spurs face Newcastle and Leicester next in the Premier League before the first leg of their Champions League last-16 tie against Borussia Dortmund.