Spurs had breathing space three minutes after the restart when Harry Kane recovered from losing his footing to convert Trippier's cutback for his 27th league goal of the season.
Watford continued to create opportunities and only a fine night's work from Hugo Lloris prevented this from being a banana skin in Tottenham's Champions League pursuit.
Relive how the action unfolded below with Sports Mole's minute-by-minute updates.
7.00pmThe race for the top four has been revitalised this weekend with Chelsea beating Swansea City and Liverpool dropping points to Stoke City, so the pressure is now on Tottenham Hotspur to stop their end-of-season slide as Watford make the short trip to Wembley this evening. Team news coming up...
7.02pmSPURS: Lloris; Trippier, Sanchez, Vertonghen, Davies; Dier, Dembele; Eriksen, Dele, Son, Kane Subs: Vorm, Alderweireld, Aurier, Wanyama, Sissoko, Lucas, Lamela
7.06pmSpurs were disappointing in passing up another opportunity to mark their progress under Mauricio Pochettino with a trophy last weekend with their defeat to Manchester United in the FA Cup semi-final, but they make only one change as Hugo Lloris returns in goal in place of Michel Vorm.
7.08pmTottenham fans may be wanting to see more of January signing Lucas Moura before the end of the campaign, with the Brazilian having impressed in flashes since joining from Paris Saint-Germain, but Son Heung-min gets the nod as the fourth attacker ahead of Moura and Erik Lamela.
7.10pmA calf problem sidelines Danny Rose for a fourth successive game. The left-back has been tipped to leave Spurs in the summer, as has Toby Alderweireld as the Belgian defender, amidst a contract stand-off, has to make do with a spot on the bench again as Davinson Sanchez starts.
7.12pmHarry Kane scored eight goals in his final four Premier League matches last season, and must do something similar this term to overhaul Mohamed Salah in the race for a third successive golden boot. Kane currently has 26 goals, while Liverpool's Egyptian King has a whopping 31.
7.14pmThe England striker has endured a tricky few weeks on the back of that 'claimed' goal against Stoke, which has made him the butt of the jokes all over social media, including remarkably from the official FA Twitter account, something which Pochettino rightly labelled as a "disgrace".
7.16pmIf Kane is to make a mockery of his critics, then the supply line is most likely to come from Christian Eriksen, who has enjoyed a career-best season at Spurs with 10 goals and 10 assists in the Premier League. Only Leroy Sane and Raheem Sterling have reached double figures in both.
7.18pmOnto Watford, who make three changes from the 0-0 draw with Crystal Palace and it is a new-look attack with Kiko Femenia, Richarlison and Andre Gray replacing Stefano Okaka and Roberto Pereyra, both of whom are absent through injury, and Troy Deeney in the front three.
7.20pmThis marks Gray's first start since January 13 in an underwhelming debut season following his £18m arrival from Burnley. The 26-year-old has only managed four goals in 28 outings, but two of those came in his most recent two starts, which begs the question why he's been on the bench this whole time?
7.22pmRicharlison is on an even longer goal drought than his teammate, having gone 23 league games without a goal after intially notching six in his first 12 matches to apparently attract attention from Watford's opponents tonight. His recent form might have seen Spurs look in another direction!
7.24pmThe Hornets have on-loan Barcelona winger Gerard Deulofeu available again after a throat infection and the Spaniard makes the bench, but it is too soon for Nathaniel Chalobah who is back in training after a long-term knee injury. Former Spurs captain Younes Kaboul and Tom Cleverley also remain out.
7.26pmWatford are following their familiar pattern of starting the season with great promise so that they can take an early holiday. Javi Gracia led the Hornets to three wins from his first five matches but it is now six without victory, and their barren away run is even worse, stretching back 10 matches.
7.28pmIn fact, the Hornets only have one point from their last 10 league matches away from home - a 0-0 draw away at Stoke in January - which has been followed by four defeats without scoring.
7.30pmIt was the recalled Andre Gray at the Etihad Stadium of all places who scored Watford's last away goal, a whopping 638 minutes ago. Under Marco Silva earlier in the season, the Hornets strung together a run of seven straight away league matches in which they scored two or more.
7.32pmWatford's travel sickness gets even worse on short journeys to the capital, having lost their last seven league matches in London since beating Arsenal in January 2017, conceding 20 in the process.
7.34pmSTAT: Could this be a Premier League first? Watford's 14.2 mile journey from their training ground to Wembley is actually shorter than that of the home side, with Tottenham's complex 20.9 miles away from their temporary home, in which they have three league matches remaining.
7.36pmAlthough they have not been struck by the Wembley curse that once threatened to derail their entire season, Spurs have lost their last three matches at the home of football - against Juventus and the Manchester giants. However, it is only one defeat in 15 league matches at Wembley for Poch's boys.
7.38pmWith the FA Cup semi-final not strictly counting as a home fixture, the two successive defeats on their own patch is as many as Tottenham suffered in their previous 42 combined. They have not lost three in a row at home in the same season since a run of four losses back in November 2004.
7.42pmHEAD TO HEAD: Tottenham are unbeaten in 12 meetings with Watford in all competitions since a 3-2 defeat at White Hart Lane in the League Cup in October 1994, winning nine of those matches.
7.44pmWatford have lost their last seven away league matches against Spurs since a 5-1 win in May 1985 under the late Graham Taylor, but they did hold them to a point at Vicarage Road in December when Sanchez was sent off.
7.46pmNot only has the top-four race been opened up by this weekend's results, but so has the relegation battle of which Watford aren't quite clear of. Southampton's win over Bournemouth has brought the Hornets to within six points with three to play, so they aren't mathematically safe yet.
7.48pmThings could be getting a little nervy too for Spurs, who might have thought that they had wrapped up Champions League qualification for a third successive season with victory at Chelsea last month. However, three Chelsea wins in a row have cut the gap from eight points to two.
7.50pmThe Premier League season is winding down, and so are thousands and thousands of Fantasy Football Leagues across the world. Nearly 18% of players are looking for a big performance from Kane tonight (although I need some Dele Alli magic myself!)
SCOUT: All eyes on Kane, who is the 2nd top captain pick (17.84%) for GW36, with 54 of the top 100 #FPL managers handing him the armband. He was the most bought player for GW36, transferred in by 241,417#TOTWATpic.twitter.com/WJdxloA6Fc— Fantasy Premier League (@OfficialFPL) April 30, 2018
7.52pmWhile Kane is on a poor run, of his standards at least, of two goals from eight games, Eriksen is a man in form having been directly involved in eight goals in his last seven games in all competitions.
7.54pmJust over five minutes until kickoff at Wembley, where Michael Oliver is our referee tonight. There will be no English official at the World Cup this summer which will be a disappointment to Oliver who is arguably the pick of the bunch in the Premier League.
7.56pmPREDICTION: Tottenham cannot afford a slip up tonight and they haven't had many this season against bottom-half teams. I think they will have enough tonight to claim a 2-0 win, and it could be more if Spurs get an early goal and get Watford's players dreaming of sandy beaches again.
7.58pmLineker has got the bantz going on Twitter tonight. Anything better than another Harry Kane joke...
Nothing to say yet about the game, but just had to use the hashtag #TOTWAT— Gary Lineker (@GaryLineker) April 30, 2018
1 minKICKOFF: We are underway at Wembley which is far from at full capacity on the back of some home heartbreak. England boss Gareth Southgate has made the effort to come out though...
3 minKane finds room for a shot on the edge of the box but he strikes it like a man bereft of confidence as Oscar Karnezis, an ever-present in goal for Watford under Gracia, collects his left-footer with ease.
5 minFormer Spurs midfielder Capoue is guilty of not following the run of Eriksen who gets to the right byline to win a corner, from which Kane runs onto the ball nicely but heads it against Mariappa, with Son flagged offside from the second ball.
7 minThe hosts have another corner as Mariappa clears an inviting Trippier cross behind at the back post. Dier, who is yet to score this season, meets it with a header but cannot direct it on target.
9 minIt has been all Tottenham in the opening stages although Watford have just had their first taste of a counter-attack through Femenia, whose progress down the right is halted by Vertonghen. With the pace of Femenia, Richarlison and Gray that is probably Watford's best route to goal this evening.
11 minAlli picks up a loose pass from Capoue and drives forward into the left edge of the area before pulling the ball back for Kane, whose first touch is very heavy and denies him a shooting chance.
13 minCapoue has made a shaky start to his 100th appearance for Watford. The Frenchman was sold by Pochettino to Watford after being one of Andre Villas-Boas's infamous Magnificent Seven.
15 minThere have been a couple of decent openings for Watford in the last couple of minutes, with Richarlison slipping when attempting to square to Gray and Femenia miscontrolling a cross from Hughes at the back post, when he may have been better taking on the first-time half-volley.
16 minTottenham have been gifted an opening goal by an absolute howler from Karnezis, who spills a Trippier cross into the path of Eriksen, who lifts the ball over the scrambling goalkeeper to Alli for a simple two-touch tap in. It was a good cross from Trippier but should have been easy pickings.
18 minSome concern here for Spurs as one of the men who played a role in that goal - Trippier - requires treatment after being caught on the ankle by Holebas. The full-back limps off the pitch but should be okay to continue, which will be of relief to the onlooking Southgate too.
20 minSpurs move the ball quickly on the edge of the Watford box with Son teeing up Dier for a 25-yard piledriver which was always rising over the crossbar. The England international, who has started 98 of Tottenham's last 102 league games - seems in the mood for a goal tonight!
22 minRicharlison cuts back onto his right foot to deliver a cross which he badly overhits, as it drifts straight behind for a goal kick. I'm not sure that is the type of service that Watford will be looking for this evening anyway, with Troy Deeney having dropped out for Gray.
24 minA Spurs attack is pulled up for handball by Son as he tried to control the ball on his chest. The South Korean loves playing against the Hornets - with four goals in six matches.
26 minCHANCE! Dier's slack pass presents Watford with a chance as Capoue weighs his through-ball to Gray perfectly. The striker has to take the shot on early under pressure from Vertonghen and gets plenty behind a toe-poke which Lloris keeps out with a strong save.
28 minTrippier does not seem to have quite run off that earlier knock and that might be why he is off balance as he tries to steer a volleyed cross into the path of Kane at the near post. That is a skill that the England international possesses but he got it badly wrong there to send it straight behind.
30 minSon is growing into the game in the last few minutes but he has been well marshalled by Watford so far, with firstly Kabasele and then Richarlison holding him off in the box. Moments later the South Korean wants a penalty for a push by Kabasele but it would have been very soft.
32 minThe hosts break in numbers with Eriksen leading the charge through the middle. He tries to set up Alli with an acute chip over the Watford defence but Karnezis is off his line quickly to claim, cleanly this time, before the goalscorer can stretch out a foot.
34 minThey may lead 1-0 but Tottenham have been far from their best so far. Their passing has not been as crisp and precise as it usually is and so far their only clear-cut chance was gifted to them by the opposition goalkeeper. Confidence may have been hit but three points tonight would do wonders.
36 minSHOT! A delightful flick from Hughes splits the Spurs defence and finds Doucoure, who works the ball onto his right foot for a powerful shot which is well held by Lloris from 12 yards out.
38 minThe hosts have looked semi-dangerous from set pieces tonight and Vertonghen has two bites of the cherry here, winning the first header before seeing his follow-up effort blocked by Cathcart.
41 minA drop of the shoulder gets Hughes, who is having an increasing influence on proceedings, away from Dembele and he picks out Richarlison in space down the left. The Brazilian, desperate for a goal, cuts inside and tries to get a shot away but Trippier gets close enough to him to make the block.
43 minSAVE! Lloris has to make his third good save of the half as he pushes away a Richarlison drive, left-footed across the goalkeeper, after Gray had picked out a pass to release the South American.
44 minAnother nervy moment for Spurs at the back as Lloris races 40 yards off his line to meet the run of Doucoure. Thankfully for his teammates, the Frenchman wins the 50-50 by knocking the ball out for a throw-in.
8.50pmTottenham may be relieved to hear the half-time whistle because, while they are 1-0 up at Wembley, they were looking shaky in the final 10 minutes of that half. If Watford have not been the better team, they have certainly had the better chances and are arguably unfortunate to find themselves behind.
8.52pmThat opening 45 minutes was the story of two goalkeepers, with Oscar Karnezis gifting Dele Alli a 16th-minute goal before Hugo Lloris made a series of good saves to retain Tottenham's lead. Spurs's captain has made some errors recently but he has been on the money so far tonight, and has had to be.
8.54pmIt is now seven minutes short of 10 hours since Watford scored an away league goal, and a lack of match sharpness and confidence was evident in Gray and Richarlison's attempted finishes. Had it been October, the Hornets might have found themselves 2-1 ahead at the break.
8.56pmThat is an incredibly random selection of players, but the point still stands that 37 Premier League goals in 102 games is mighty impressive for a young midfielder.
8.58pmBENCH WATCH:Javi Gracia will be tempted to keep it the same considering how his side finished that first half, although Deulofeu is in reserve if he wants an attacking upgrade on Femenia. Dembele has been sloppy for Spurs so we might see Victor Wanyama before long.
9.00pmSTAT: Tottenham are one of only two teams with a 100% record when leading at half time in the Premier League this season, with Manchester United the other side to boast that impressive conversion rate.
46 minKICKOFF: The second half is underway with both managers sticking with the same teams for now...
48 minThe half-time anxiety is taken out of Wembley by a goal three minutes after the restart from Kane, who slips when trying to meet Son's original cross, but is back on his feet to knock hope the second ball from Trippier from eight yards out. It all started with a lovely pass from Alli into the left channel for Son.
50 minThat league goal moves Harry Kane onto 27 for the season - within four of Mohamed Salah now.
52 minAnother intelligent pick out from Alli nearly releases Son, who is held up and had to shift the ball out to Trippier who is being afforded way too much space by Holebas. This cross is aimed towards Alli's near-post run but Karnezis gathers it safely.
54 minTrippier is having a field day here and his lethal combination with Kane would have yielded another chance had Kabasele not come across to make an important intervention in the six-yard box.
56 minDier switches the play to Davies and, via Eriksen, is teed up for another rasper from range but Mariappa is in the way this time. His last Spurs goal came against Watford in April 2017.
58 minThe match is going to a sloppy period, very similar to that which followed Tottenham's goal in the first half. Spurs can't switch off here so they can make the most of this win and take some momentum into the rest of their run-in.
60 minRicharlison skins Trippier down the outside and his cutback is into a really dangerous area, but PFA Team of the Year member Vertonghen was in the right place at the right time to clear.
62 minSUBSTITUTION: Mousa Dembele has required some attention from the Spurs physio and Pochettino isn't going to take any chances, bringing on Wanyama in place of the Belgian.
64 minYELLOW! The Kenyan midfielder is straight into Michael Oliver's book, although he is very unlucky to see yellow for a 50-50 challenge in which Richarlison studded him in the thigh.
66 minSUBSTITUTIONS: Gracia has made a couple of changes of his own in the last few minutes, replacing Femenia and Gray with Deeney and Deulofeu which should provide Watford with more of a cutting edge.
68 minPOST! Vertonghen's five-year wait for a Premier League goal goes on as he heads a wonderful Trippier delivery from a free kick against the post, with Kane unable to sort out his feet in time to tap home what should have been a simple rebound. Vertonghen shakes his head in disbelief!
69 minWatford counter nicely but Deeney chooses the wrong option of turning back on himself to pass to Richarlison when Hughes was wide open to his right. That is a decent chance gone begging.
70 minMISS! Deeney this time provides the perfect set up, getting above Davies at the back post and knocking down for Richarlison, who cannot get over his volley from eight yards out and sends it high over the crossbar. It is a terrible miss from the out-of-form Brazilian.
72 minDeulofeu rounds Lloris and slots the ball into the net, but the offside flag had already been raised against the Spaniard. It was a very marginal call from Doucoure's inch-perfect through-ball.
74 minDISALLOWED! Now it is Tottenham's turn to have a goal ruled out, and it is a shame because the control and pass from Vertonghen to set up was absolutely sublime. The striker finished expertly into the bottom corner but had gone half a yard early.
76 minSUBSTITUTION: Pochettino makes his second change but it is not the one that Spurs fans may have wanted as Lucas remains rooted to the bench. Sissoko is on in place of Son who has not been too effective outside of a five-minute spell in the first half.
78 minThere is a long stoppage in play as Trippier and Richarlison receive treatment following a clash of heads. The Spurs man is okay to continue but Richarlison needs patching up on the touchline before continuing, if he does indeed return to the field after a cut above the eye.
80 minRicharlison is back on but the break in play came at a bad time for Watford who were starting to apply some pressure on Spurs as they did at the end of the first half. That momentum has been lost and now Tottenham look like seeing out a crucial three points.
82 minSUBSTITUTIONS: Pochettino is making Lucas work for every minute he is going to get at Spurs! Erik Lamela is Tottenham's preferred third substitute as Dele Alli makes way. Meanwhile, Watford's final change sees Andre Carrillo replaces Will Hughes, who has been bright in patches.
84 minEriksen tries to run onto Sissoko's pass into the right channel but Kabasele comes across to quell the danger.
86 minLamela has embarked on a couple of eye-catching dribbles in his brief cameo but there has been no end product thus far. The Argentine takes too many touches here, missing the opportunity to play Kane in behind.
88 minKabasele gets caught underneath a Lloris punt forward but recovers well to force Lamela wide from the penalty spot to the corner flag, and the danger goes with him. Lamela might have had more touches in his six minutes than Andre Gray had during nearly an hour on the pitch!
90 minCHANCE! Kane feeds Sissoko to his right but the Frenchman shoots a couple of yards over the bar from a great position to score a third which would have flattered Tottenham on the night.
90+2 minSHOT! Tripper's poor clearing header drops nicely for Deeney but he can't quite keep his volley down. There will be six minutes of added time following the Trippier-Richarlison stoppage.
90+4 minSAVE! Lloris completes a good night's work on his behalf with a good close-range block from Carrillo, who had danced past Davies and into the box to get a powerful shot away.
9.58pmThey certainly weren't at their best, but Tottenham pick up three crucial points in the race for the top four, moving five clear of rivals Chelsea which almost sees them over the line. Dele Alli and Harry Kane with the goals for Spurs, but Watford could have come away with something on another night.
10.00pmThat's it from our coverage at Wembley. You can read our match report here, and check the updated Premier League table here. Be sure to rejoin Sports Mole this week for live coverage of the Champions League semi-final second legs. Until then, goodbye!