A narrow win at Vicarage Road meant the Foxes extended their lead at the top of the Premier League to five points.
Tottenham and Arsenal dropped points in the North London derby to give Claudio Ranieri’s side a chance to strengthen their title bid, and it took a bit of brilliance from Riyad Mahrez to do so.
It was a strong start from the visitors as Jamie Vardy went close on a number of occasions but the two sides went in level at the break, after a tepid end to the first half.
This forced Ranieri to make two changes ahead of the second period; Andy King and Jeffrey Schlupp replaced Shinji Okazaki and Marc Albrighton.
The Tinkerman, as he is known, has been extremely consistent with his team selection this season but his substitutions changed the game in the Foxes’ favour as they began to boss the midfield and pose more of a threat on the attack.
Only ten minutes of the second half had passed when Leicester opened the scoring. A Christian Fuchs cross was headed out to the feet of Mahrez, who faked the shot to open up some space before exceptionally firing the ball into the top left corner.
Mahrez has now been involved in 26 goals this season; 15 goals and 11 assists for the Algerian, more than any other player.
Watford had a couple of chances in the game but Troy Deeney and Odion Ighalo failed to find the net, ensuring Leicester kept their tenth clean sheet of the campaign.
The away form of Ranieri’s side is largely due to their swift counter-attacking style and they have now picked up 31 points on the road this season, five more than any other side.
If the Foxes are going to win the Premier League title they are going to have to replicate the form of last season when they won seven of their last nine games to evade relegation against all odds.
At this stage of the season last year they were still rooted to the bottom of the table with 41 points short of their current tally.
Leicester welcome Newcastle United to the King Power Stadium in the next fixture; a key game as the Magpies are battling for their top flight status.