This being an Old Firm derby, there was no lack of intensity, and more than a hint of controversy. Celtic utterly dominated in the first half, but their finishing was poor. They also had a shout for a clear penalty denied when Ehiogu brought down Aiden McGeady.

Rangers were far better in the second half, getting the upper hand with an urgent pressing approach that became more fluent and attractive the more their confidence grew.

Celtic ended up frustrated, demonstrated most clearly at the end when their captain, Neil Lennon, reacted furiously to something shouted by a home fan. Lennon hurled an empty plastic bottle in that general direction, although, given that it landed in an empty dug-out, there seemed no intent to hit anyone.

Rangers have now won six and drawn one of their seven SPL games since Walter Smith took over as manager from Paul Le Guen. Yesterday's victory means they have closed the gap on their Old Firm rivals to a mere 16 points and Celtic must wait a fortnight at least to seal the title.

Rangers maintain their firm hold on second place in the table - and the second Champions League spot for next season - ahead of Aberdeen, who visit Ibrox on Saturday.

"I can't remember the last goal I scored, it was several years ago, two or three at least," Ehiogu said. "So to score one like that today, to settle the match in such a fashion in my first Old Firm game, you couldn't ever have scripted that.

"It actually felt a bit surreal," he added. "Lying upside down after striking the ball, I thought at first that it had been saved. Then even when I heard the roar, it took a few moments to sink in."

Ehiogu, 34, and David Weir, 36, were both signed by Smith in January and have defied their years to form a fine central defensive partnership. Both were superb yesterday.

"We rode our luck a bit in the first half," Smith said. "But the whole team played well after that. Not many teams come here and win. Even some of the bigger European sides [including Manchester United and Milan] have come here this season and not won. So you have to be pleased."

Rangers' next match is on Wednesday, when they face Osasuna in Pamplona in the second leg of their Uefa Cup last-16 tie.

The Celtic manager, Gordon Strachan, said he was "very pleased" with his team's performance, if not the finishing. Kenny Miller, Shunsuke Nakamura, Evander Sno and McGeady all had more than one chance to score.

Ehiogu's winner arrived after a corner and four keepy-uppy headers, three of them by team-mates.

Goal: Ehiogu (50) 0-1.

Celtic (4-4-2): Boruc; Wilson, Pressley (O'Dea, 78), McManus, Naylor; Nakamura, Lennon, Sno (Riordan, 81), McGeady; Vennegoor of Hesselink, Miller (Jarosik, 74). Substitutes not used: Brown (gk), Beattie, Perrier Doumbe, Caldwell.

Rangers (4-5-1): McGregor; Hutton, Ehiogu, Weir, Murray; Novo (Rae, 90), Thomson, Hemdani, Ferguson, Adam; Sebo (Prso, 74). Substitutes not used: Klos (gk), Boyd, Papac, McMillan, Furman.

Referee: S Dougal.

Booked: Celtic Lennon, Sno; Rangers Adam, Ferguson, Novo.

Man of the match: Ehiogu.

Attendance: 59,425.