Kevin Thomson's first goal for Rangers after 14 months at the club settled the most significant Old Firm derby in years, and sent his side six points clear of Celtic with a game in hand.
If the title race is not over, then this certainly signifies the beginning of the end for Celtic, and, maybe, given the harsh judgements often handed down to Old Firm managers who finish a season without silverware, for Gordon Strachan.
Rangers remain on course for a quadruple. This was their 13th consecutive League win, and a fourth straight derby victory to nil over Celtic. They already have the CIS Cup in the trophy room – their first pot since 2005 – and are in the quarter-finals of the Scottish Cup and the Uefa Cup.
Thomson struck in the final minute of a first half that Celtic dominated. Scott Brown stum-bled on the ball with only Allan McGregor to beat, wasting Celtic's clearest opportunity. McGregor had already thwartedGeorgios Samaras and later made a fine save from Andreas Hinkel before Thomson made a surgingrun into the visitors' area, played a neat one-two with Jean-Claude Darcheville to bypass defenders who then failed to track him, and slammed a right-foot shot at a tight angle past Artur Boruc.
The hero of the day failed to last the 90 minutes, leaving on a stretcher with 13 minutes remaining. He had sustained the shin injury that caused his departure by pushing forward and making a mess of a challenge on Samaras in the Celtic box. Thomson had been booked earlier, for dissent, and he arguably deserved a second yellow, either for the challenge or simulation in an attempt to win a penalty.
With Celtic chasing the game, Rangers looked likelier to score the game's second goal. Barry Ferguson had a shot deflected, Thomson had a 35-yard free-kick held, and Charlie Adam's injury-time shot needed a smart save from Boruc to keep it out.
"We're obviously delighted to win," said the Rangers manager,Walter Smith. "It was important to win today because we've got two visits to Celtic still to come." The next derby is at Celtic Park on 16 April, and the last of the season at a date yet to be decided.
Strachan, asked about Celtic's chances of winning the title now, said: "It's going to be very difficult." He added: "I think a balanced person's view is that we did enough to win, or at least not get beaten. It's come back to bite us, getting chances and not taking them."