After a pounds 31m refit, the theatre opened its doors to a performance of Stanley Houghton's turn-of-the-century potboiler Hindle Wakes - the play whose run was halted by the bomb.
As a sell-out audience started to pour into the theatre, Alan Burrough, a security guard, said: "Over the past two-and-a-half years it is the ordinary public we have missed.
"Today we have had people coming in saying, `Hello again, Alan.' That's what we've been missing. The atmosphere here is great," said Mr Burrough, who cleared people from the theatre on June 15, 1996, after police received a bomb warning.
He helped direct up to 20 people to safety from the theatre and box-office a few minutes before the bomb exploded. "Not only could we hear the blast, we could actually see it," added Mr Burrough, who remembers taking shelter from the explosion in a shop doorway.
The bomb destroyed all three of the 19th-century building's glass domes. At one point, engineers doubted whether it could be saved.
But thanks to the largest award outside London from the National Lottery's heritage fund, the building now boasts a new blue glass dome, rehearsal rooms and a separate studio with seating for 120 people.
There is also a new roof that allows scenery to be hoisted more easily. When the company performs King Lear with Tom Courtenay later in the season, it is planned that the new roof will be opened to the gods.
"In one sense, the bomb has allowed us to refurbish in a way that would not have been possible otherwise," said John Goodfellow, the theatre's senior spokesman.
"The atmosphere here today has been magical. I think it is certainly the most important day for the company since it was founded in 1976.
"But it is also important for Manchester. The theatre was very close to where the bomb went off and it is the first of the major reconstruction projects to be completed in the city."
Many members of the original cast, including the actress Sue Johnson, returned yesterday to take their parts in the play, which was halted after only eight performances when the bomb exploded, causing damage estimated at pounds 200 million in central Manchester.
During the refurbishment work, the company has been staging performances in a tented building across the city at Upper Campfield.Reuse content