The Phantom, played by Ramin Karimloo, right, performs a scene with Christine, played by Sierra Boggess, from Love Never Dies, at the Adelphi Theatre in central London. ((Joel Ryan/Associated Press))

Love Never Dies, Andrew Lloyd Webber's long-awaited sequel to Phantom of the Opera premiered in London Tuesday evening to mixed reviews by critics.

Phantom, the popular musical that first opened in 1986, still runs in London's West End and some its many fans have expressed outrage at the thought of a sequel.

Lloyd Webber acknowledged in an interview with Variety that it is a problem to manage expectations on a project like this one, but said he "didn't go into it lightly."

Most critics found Love Never Dies matched the lustre of the original Phantom in its production values and its score.

But Michael Billington, reviewer for the Guardian, said the sequel lacked the "narrative tension" of the original.

"There is much to enjoy in Andrew Lloyd Webber's new musical," he wrote. "The score is one of the composer's most seductive. Bob Crowley's design and Jack O'Brien's direction have a beautiful kaleidoscopic fluidity. And the performances are good. The problems lie within the book, chiefly credited to Lloyd Webber himself and Ben Elton, which lacks the weight to support the imaginative superstructure."

Ramin Karimloo, the Canadian star of Phantom in the West End, has moved into the role of the deformed mask-wearing composer in the new tale, set 10 years after the original.

Now he's the impresario of a Coney Island fun fair and lures his muse Christine back for a new bid at stardom under his tutelage.

All has not worked out well for Christine — her beloved Raoul has problems with drink and gambling and she has a son in tow. He turns out to have been fathered by the Phantom, a twist several critics found implausible.

Many critics praised performances by Karimloo and Sierra Boggess as Christine, but Benedict Nightingale at  the Times of London took issue with Karimloo's portrayal.

"The 'poisoned gargoyle who burns in hell' has clearly taken an anger management course in New York," Nightingale wrote. "True, he fills his eyrie with oddities, like the skeleton who pushes a cocktail trolley, but he's very much the considerate gentleman, eager impresario and, soon, doting father.

"Would he whimsically hang the backstage crew or send a chandelier crashing into a crowd? Not anymore."

That view was far from unanimous.

The Daily Telegraph's Charles Spencer said  Karimloo and Boggess "sing superbly … with a real spark between them" and Paul Taylor  in the Independent gave it five stars.

Taylor praised both the technical excellence of the show, the "superb orchestra" and "Lloyd Webber's dark-hued, yearning melodies."

The opening night audience also enjoyed the spectacle, giving it a standing ovation.

Lloyd Webber said it often takes time for a show to "settle down."

The Phantom itself got mixed reviews when it opened, but audiences couldn't get enough of it.