Nicolas Otamendi was the surprise hero as Manchester City secured a 2-1 derby win over Manchester United to move 11 points clear at the top of the Premier League table.
The Argentina defender struck in the second half after Marcus Rashford cancelled out David Silva's opener, ensuring a record-equalling 14th win in a row in the top flight for Pep Guardiola's side.
United took a 40-game unbeaten home run, including a 100 per cent record this season, into the match, but City were the dominant force from the outset and deserved the lead Silva secured in the 43rd minute.
City's first chance fell to Raheem Sterling, who shot straight at David de Gea, before Gabriel Jesus produced a similarly tame finish after surging clear into the penalty area past Marcos Rojo.
De Gea made his first real save of note four minutes before the interval, tipping over Leroy Sane's effort from close range, but it proved a futile piece of agility as City snatched the lead moments later.
Lukaku misjudged his header from the resulting corner and the ball fell kindly to Silva, who prodded home from inside the six-yard box.
The goal seemed to spark United into life suddenly, with Martial at last testing Ederson, and they snatched an equaliser in first-half injury time when Rashford pounced on Fabian Delph's failure to clear and slotted home from 12 yards out.
But City regained their lead nine minutes into the second half in remarkably similar fashion to their opening goal. Lukaku's attempted clearance from Silva's free-kick went straight against Chris Smalling and fell to Otamendi, who steered the ball acrobatically into the net.
City's control of the ball showed no sign of waning and De Gea was called upon to make a fine low save to deny Kevin De Bruyne, although Rashford stung the palms of Ederson after another Delph error as Mourinho turned to substitute Zlatan Ibrahimovic for hope.
Ederson pulled off a brilliant double save to deny Lukaku and Juan Mata six minutes from time, depriving United of a second equaliser and putting the title race firmly in City's grasp as they became the first side to win 14 consecutive top-flight games in a single season.
Meanwhile, Wayne Rooney scored a late penalty as Everton claimed an unlikely 1-1 draw against a dominant Liverpool at Anfield in the Merseyside derby.
Charlie Austin surprised the Arsenal defence with an early goal, however at the tail end of the match Olivier Giroud brought things level with a header (Arsenal vs Aouthampton).
The below are the results of the 16th round matches and the standings of Premier League.
The result of the 16th round match in Premier League Source: Google
Ranking after the 16th round match of Premier League Source: Google
