It was yet another scintillating performance on the road as City also set a new Club record in the process.
It was a similar story after the re-start, with Bernardo scoring a sumptuous third to seal victory just past the hour.
It was a blistering start by the champions.
The home side barely had a touch as City moved the ball around with speed and purpose, stretching Watford from right to left and mercilessly pinning them in and around their own box.
Within the next six minutes, Jack Grealish could have scored another two goals.
First he arrived unmarked to head a corner point-blank at Bachmann – either side of him would surely given the goalkeeper no chance – and moments later he collected another fine Foden cross but saw his shot beaten away by the Watford No.1.
But if Jack was down about those misses, he didn’t let it affect his game and he was heavily involved in City’s second of the evening.
His ball from the halfway line found Ilkay Gundogan who played a one-two with Bernardo before seeing his shot saved – but Bernardo was first to the loose ball, skipping past two challenges in a blink before beating Bachmann on his near post to make it 2-0.
It was a fifth Premier League goal in eight games for the Portuguese who can do no wrong.
Watford improved in the second-half, but City continued to create chances.
On the right of the Hornets' box, he received a pass from Kyle Walker, cut inside a challenge before curling a powerful drive into the top left corner - a thing of beauty - and his sixth in eight Premier League games.
The only blot on City's copybook came on 74 minutes when Chucho Hernandez fired a crisp low drive past Ederson whose wait goes on for his 100th clean sheet in sky blue.
Bernardo on fire
Bernardo Silva - it's actually hard to find superlatives that do him justice these days.
His two goals were superbly taken, as was his all-round performance (yet again).
The irrepressible midfielder is at the very top of his game and now enjoying his best ever season with the Blues.
And given what has gone before, that is some accolade.
Phil Foden’s progress from talented teenager to first team regular and England international has been seamless.
But the 21 year-old has now shifted up another gear.
Full of energy and invention, his delivery and ability to pick a pass gets better and better.
Indeed, he has become irreplaceable and, you would imagine, one of the first names on the team-sheet when fit.
As a footballer, he is also a genuine pleasure to watch.
WATFORD: Bachmann, Femenía, Troost-Ekong, Cathcart, Rose (Ngakia 71), Louza (Hernandez 46), Dennis, Cleverley (Kucka 46), Sissoko, João Pedro, King
Subs: Gosling, Fletcher, Tufan, Kabasele, Elliot, Morris
11 - Against no side has Raheem Sterling scored more goals in his professional club career than he has against Watford (11, level with Bournemouth). Legs. #WATMCI— OptaJoe (@OptaJoe) December 4, 2021
STAR MAN: Bernardo
What it means...
City go to the top of the Premier League for the first time this season, moving two points ahead of Chelsea and one point ahead of Liverpool.
City travel to Germany to face RB Leipzig in the final Champions League group stage match on Tuesday (17:45 GMT).
With top spot in Group A already secured, Pep may well use the game to field one or two players who haven't had as many opportunities to start this season as others.
Then, next Saturday lunchtime, the champions host Wolves (kick-off 12.30pm).
"Everyone is back, it doesn’t matter who plays, we are consistent and winning games but in football everything goes down in one second.
"More than pleased with what the guys have done in this tough period and now comes the toughest one for amount of games, weather, injuries.
"We keep going with this rhythm and try to play good."
Stats and facts
The 3-1 win over Watford on Saturday means City have set a new Club record for top-flight league victories in a calendar year. It was the Blues' 31st league win in 2021, surpassing the previous record of 30 set in both 2017 and 2019.
City are unbeaten in the last 19 meetings with Watford in all competitions (W17 D2), netting 62 goals in this run. Only against Norwich (22 between 1965-1981), Walsall (19 since 1897) and West Brom (19 since 2010) have the Blues ever had longer unbeaten runs.
City have never lost to Watford in the Premier League (W11 D2), winning our last 11 against them by an aggregate score of 40-5.
Pep Guardiola has won all 10 of his meetings with Watford in all competitions, by an aggregate score of 42-4. Against no side does the Catalan have a better 100% win rate in his managerial career (also 9/9 vs Bournemouth).
City haven’t lost any of the last 11 matches in all competitions in the month of December (W10 D3). Across those 11 games we have scored 20 goals and conceded only four.
City have won each of the last nine away games on Saturdays in the Premier League, scoring 19 times and conceding only twice.
City have lost just two of our last 22 Premier League away games (W18 D2), going unbeaten in each of our last seven on the road (W6 D1). Since Pep Guardiola’s first season in charge (2016-17), City have won more away games (73) and away points (230) than any other side in the Premier League.
Raheem Sterling has been involved in 13 goals in just nine games against Watford in all competitions (11 goals, 2 assists). Only against Bournemouth (11) has Sterling scored more goals in his senior club career than he has against the Hornets.
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