Tottenham keeper Paul Robinson scored a remarkable goal from fully 80 yards as the hosts moved up to sixth with a fine win that piled the pressure on Watford.
Paul Robinson celebrates his stunning goal at White Hart Lane
Jermaine Jenas handed Spurs the lead, heading home Pascal Chimbonda's cross, before Robinson made it two when his long free-kick bounced into the corner.
Jermain Defoe twice went close and Mido contrived to miss an open goal as Spurs tormented the toothless Hornets.
Hossam Ghaly curled a third late on before Darius Henderson's consolation.
The Hornets' goal in injury-time marred an otherwise comfortable afternoon for Tottenham, and meant the hosts have now gone 20 Premiership games without keeping a clean sheet.
But, with Monday's FA Cup quarter-final against Chelsea looming, Martin Jol could have barely hoped for a better day's work from Tottenham.
And it was all the better given his team selection, which saw key stars Dimitar Berbatov, Aaron Lennon and Robbie Keane left on the Tottenham bench, with Didier Zokora rested altogether.
For his part, Watford boss Adrian Boothroyd erred on the side of a numbers-behind-the-ball tactic and for much of the half it worked, with Spurs struggling to break through.
The visitors' aggressive intent was evident from the outset and Riccardo Rocha was forced off field for seven minutes to have four stitches in a wound under his eye.
However, despite lacking the fluidity and potency of recent weeks, Spurs were in total control and Robinson was a virtual spectator throughout the first half.
Still, though, a Mido half-chance and Jenas long-shot aside, it took until the 41st minute for Spurs to find a meaningful chance - but when they did, it counted.
Chimbonda launched the ball to the back post from the right touchline and Jenas rose under severe pressure to guide a splendid header into the corner for his fifth goal in his last seven games.
Suddenly, Spurs found their attacking verve and Defoe almost made it two when he twisted and turned Lloyd Doyley before toe-poking narrowly wide from 16 yards.
Boothroyd replaced Tamas Priskin with Henderson in the second half, but it made little impact and Defoe's delightful chip narrowly drifted wide before Mido firmly headed at Foster as Tottenham continued to threaten.
Goalscorer Robinson, right, consoles Foster after the final whistle
However, few would have predicted the nature of Tottenham's second when it came.
Robinson lined up a free-kick from five yards outside his own penalty area, but his hoof floated over the defence, bounced over Foster, and drifted into the corner.
It was exactly the sort of freak goal that goes against teams when they're struggling, and it was almost even worse when Foster had to turn over the bar from Tom Huddlestone's crashing 20-yard drive.
It should definitely have been three minutes later, when Foster spilled Huddlestone's effort only for Mido to somehow allow him to save his tame effort with the goal gaping.
However, the Spurs faithful did not have to wait long for a deserved third, Ghaly curling in right at the end after a pacey counter-attack.
Henderson poked in at the last after Chimbonda's mistake to take the gloss off Robinson's day, but there is little doubt the win will last long in the memory of the Spurs keeper.
Tottenham manager Martin Jol:
"To get a goal is so nice for Robbo - and it came at a crucial moment for us as well because we needed the second after dominating for so long.
"You can say now that we really are scoring from all angles at the moment!
"We're having a dream spell - we're playing more games than any team, lots of them away from home, but we're playing well and getting victories.
"We know only too well that cup competitions can go either way and if you don't win them, you get nothing. We'll be pushing hard to win them of course, but if we don't we have to do well in the league."
Watford boss Adrian Boothroyd:
"I've never seen anything like that before to be honest, but it's a freak goal and Ben Foster will bounce back and fulfill his potential as one of the best keepers in England.
"The result was a fair one. We didn't know whether to press or attack and we got caught between two stools and against a side of that quality, they will punish you.
"I'm disappointed and we've let ourselves down. This was always going to be a hell of a task but we're still in there and we'll keep fighting and keep dreaming."
Tottenham: Robinson, Chimbonda, Dawson, Rocha, Young-Pyo Lee (Stalteri 80), Ghaly, Jenas, Huddlestone, Malbranque (Lennon 71), Mido, Defoe.
Subs Not Used: Cerny, Berbatov, Keane.
Goals: Jenas 41, Robinson 63, Ghaly 85.
Watford: Foster, Mariappa, Doyley, Shittu, Powell, Chambers (Kabba 77), Mahon, Williams (Rinaldi 62), Smith, Priskin (Henderson 56), Bouazza.
Subs Not Used: Lee, Williamson.
Goals: Henderson 89.
Ref: M Halsey (Lancashire).