Rangers took a huge step towards winning the Scottish Premiership title as Callum McGregor's own goal gave them a 1-0 Old Firm derby win over Celtic.
Steven Gerrard's unbeaten team now lead their fierce rivals by a formidable 19 points at the top of the table.
Celtic still have three games in hand but their hopes of clinching a historic 10th straight title look increasingly slim, with this result piling the pressure on manager Neil Lennon.
Champions Celtic had the better of Saturday's match at Ibrox, but the tables were turned when Nir Bitton was sent off after 62 minutes.
Callum McGregor then inadvertently gave Rangers, who did not register a shot on target in the contest, a priceless winning goal.
Celtic made an excellent start and it took two pivotal saves from goalkeeper Allan McGregor to stop the visitors from going into an early lead.
He impressively got down low to deny Odsonne Edouard, who had not played in the last meeting between the sides, which Rangers won 2-0 in October.
The Rangers keeper then produced an even better fingertip stop to tip a 25-yard shot from Leigh Griffiths that was destined to find the top corner onto the post.
Gerrard brought on Ianis Hagi – who had been dropped from the starting XI in place of Ryan Kent – at half-time, with Kemar Roofe coming off and his side gradually began to improve.
Rangers got a big boost when Bitton was dismissed after wrestling Alfredo Morelos to the ground as the striker attempted to race on to a James Tavernier pass and looked like he had a clear path to goal.
They moved in front after 70 minutes, Joe Aribo flicking a Tavernier onto Callum McGregor, whose arm deflected the ball beyond Vasilios Barkas.
Celtic substitute Mohamed Elyounoussi shot just over but there was no way back for the 10 men, who have now lost three straight league derbies for the first time since 2008.
What does it mean? Rangers in control
At half-time Celtic had racked up 11 shots to Rangers' three and it was one-way traffic.
But neither side registered an attempt on target in a more even second half that took a decisive turn when Bitton was dismissed, even though Gerrard's side continued to offer little attacking threat.
Celtic coming back in the title race looks highly unlikely now. Even if they win their three games in hand and the next two Old Firm derbies, they would be four adrift of a Rangers team who have won 14 in a row, conceding just three goals in that run.
Awesome Allan denies Celtic
It would have been a different game had Allan McGregor not starred in the early stages.
The veteran shot-stopper made three saves, the most crucial being an astounding parry to deny Griffiths – an intervention that gave a conservative Rangers team a platform to edge back into the match.
Morelos drought continues
While Rangers will be ecstatic at the result, Morelos was unable to end his poor run against Celtic.
He did force Bitton's red card, but otherwise saw all three of his shots blocked and has not scored in 12 league Old Firm derbies.
Key to Rangers' win was their ability to, aside from his early chance, contain Edouard, who had scored six goals in this fixture since his first appearance in March 2018 – more than any other player.
In-form Rangers are away to third-placed Aberdeen next Sunday, a day before Celtic must win when they host Lennon's former club Hibernian.