John Hartson went from villain to hero for quadruple-chasing Celtic with a stunning second-half winner to close the gap on their biggest rivals to just three points.

After Hartson had spurned two glorious opportunities he endeared himself to reduce the deficit at the top - with the Hoops having a game in hand.

But Celtic's quadruple hopes could have suffered a setback as winger Didier Agathe was forced to hobble off with a suspected hamstring injury just five days before the UEFA Cup clash with Liverpool.

But O'Neill savoured the moment of beating Alex McLeish for the first time in seven Old Firm matches - after Hartson and referee Mike McCurry had threatened to frustrated them.

The whistler set the tone after just a minute of play by awarding Rangers a free-kick after Lorenzo Amoruso had appeared to shove Chris Sutton from behind.

The official then missed a foul from Neil McCann on Bobo Balde just outside the box as the visitors dealt well with Alan Thompson's early cross.

McCurry sparked more fury in the 10th minute when he harshly penalised John Hartson for a foul on Craig Moore.

The Australian again escaped punishment for a foul on Sutton before Maurice Ross needed to head the ball behind after Hartson had flicked on Thompson's cross.

But Celtic missed a glorious chance to take the lead in the 14th minute when Stilian Petrov's corner was allowed to run across the face of goal before coming to Hartson, who sliced his right-foot shot wide at the back post.

McCurry had no choice but to take action a minute later when Fernando Ricksen floored Paul Lambert and was deservedly booked for his actions.

The Dutchman breathed a sigh of relief in the 18th minute when he sent Sutton crashing to the ground with a high tackle.

The referee was satisfied to award Celtic just a free-kick, but moments later he had his book out again after Moore had fouled the Englishman.

Rangers carved out their first opening of the game in the 28th minute when Jerome Bonnissel and Shota Arveladze set up Mikel Arteta, who drove just past the post from the edge of the area.

Petrov fired just wide from 22 yards after Sutton had seized on the ball following uncertainty in the Rangers defence.

The visitors were again fortunate not to be punished in the 31st minute when Hartson swivelled but he was just unable to get a decisive touch to the ball after Mjallby had headed Thompson's corner into the danger area.

But Celtic suffered a major blow in the 33rd minute when Agathe was forced to retire from the game after pulling up near the touchline and he was replaced by Momo Sylla.

McCurry waved away appeals from the home side for a penalty in the dying seconds of the half after Sutton had gone down under a tackle from Moore.

The Englishman was booked shortly after for tussling with Amoruso and Thompson had to pull him away from the referee at the half-time whistle.

Celtic should have gone ahead in the 50th minute when Hartson was gifted a free header from Thompson's corner, but he somehow put his effort wide from six yards.

The Welshman then did well to control Lennon's hopeful punt on his chest, but he swivelled and missed the ball before Thompson blazed wide from the left of the box.

Celtic left gaps as they chased the first goal and Peter Lovenkrands' right-foot drive from a tight-angle gave them a warning, but Douglas made a good save by his post.

Then Hartson made amends for his early mishaps in front of goal by emphatically firing the champions ahead.

Sutton headed Thompson's long ball into his path and the Welshman unleashed a fierce right-foot shot past Stefan Klos from just inside the box.

The typically-animated O'Neill was again spoken to by fourth official John Rowbotham after Lambert had been caught late by Moore.

McLeish replaced Bonnissel with another Old Firm debutant Steven Thompson in the 68th minute, before replacing the impressive Arteta with Claudio Caniggia.

Neil McCann was booked with five minutes left before Douglas brilliantly pushed away Amoruso's powerful long-range free-kick.

Ferguson took his frustration out on Sutton moments later before McCurry sparked celebrations among the Celtic supporters by blowing the final whistle.

Teams

Celtic: Douglas, Mjallby, Balde, Valgaeren, Agathe (Sylla 35), Lambert, Lennon, Petrov (McNamara 84), Thompson, Sutton, Hartson.

Subs Not Used: Broto, Maloney, Crainey.

Booked: Sutton.

Goals: Hartson 58.

Rangers: Klos, Ross (Konterman 84), Moore, Amoruso, Bonnissel (Thompson 68), Ricksen, Arteta (Caniggia 74), Ferguson, Lovenkrands, Arveladze, McCann.

Subs Not Used: McGregor, Malcolm.

Booked: Ricksen, McCann.

Att: 58,787

Ref: M McCurry (Scotland).