That giant and crumbling Hollywood mansion on Sunset, home to the greatest star of all, has undergone a major renovation. 

Director Jamie Lloyd has ripped out the interior walls and chucked the lavish adornments. He’s emptied the closets of Gloria Swanson’s favorite outfits and installed high-tech cameras. The house is almost unrecognizable.

Some will view the striking changes to Andrew Lloyd Webber’s musical “Sunset Boulevard,” and by extension the classic 1950 Billy Wilder film it’s based on, as trampling on what was divine. 

They’re needlessly pearl-clutching. Because what Lloyd has wisely left intact in his jolting new London revival, starring Nicole Scherzinger as that restless recluse Norma Desmond, are the sturdy bones of a timeless American tragedy.  

His gut reno is absolutely gut-wrenching.

Fame is as fleeting as it ever was. Madness is even madder. There’s blood! And, from the early sequence when struggling screenwriter Joe Gillis’ car chase is thrillingly depicted with a projected close-up on actor Tom Francis’ intense eyes, we are assured: This time will be bigger.

Of course, Lloyd, who directed “A Doll’s House” on Broadway last season with Jessica Chastain, isn’t this wildly imaginative production’s only risky choice.

Scherzinger, from the Pussycat Dolls, is about as far away from Norma type-casting as you can possibly get. She has little in common with former Normas, including the Martian-esque Swanson and Broadway’s Glenn Close, and she never bothers with an eccentric turban.

But her breathtaking, feral Norma is, nonetheless, a grand creature of showbiz who’s been shunned by Hollywood’s cruelly short attention span by the time she’s just 40 years old. 

Not content to give in to the ticking clock, Norma dons a sexy black dress (costumes and sets by Soutra Gilmour) as she desperately relives her best years when she was a megafamous silent-film actress in her teens and 20s. 

Driving home her obsession with the past, Lloyd has a Young Norma (Hannah Yun Chamberlain) dance around the stage — tantalizing and tormenting her future self.    

When Joe, so smoothly sung by Francis, winds up at the faded star’s doorstep, she begs him to help revise her terrible screenplay “Salome,” and the two begin a fraught journey to mutual destruction. 

Your average staging of “Sunset Boulevard” could be called “Waiting for Norma.” Whenever the diva exits, our brains take a pause until she blessedly strolls back on. 

Not so here. Lloyd pumps adrenaline into the scenes between Joe and Betty Schaefer (a formidable Grace Hodgett-Young), a fellow writer he falls for, with propulsive modern dancing (choreography by Fabian Aloise) and gripping tension.

Plus, there have been some shrewd cuts made to Don Black and Christopher Hampton’s book and Lloyd Webber’s score to hurry things along. So long! Farewell!

Lloyd, known for a sleek aesthetic, tosses in a slew of directorial flourishes that click and never come off as tired gimmicks, like they so often did in his “A Doll’s House.”

The rousing opening of Act 2, brilliantly matching the music’s propulsion, will be a key challenge to “Sunset” moving to Broadway — which it plans to do as soon as early as the spring or next fall.

Norma famously says, “We didn’t need words — we had faces,” and that is very much the mantra of this projection-heavy staging that blows up every twitch and blink. With black-and-white projections, cameras zoom in on these actors’ stunning visages. 

Francis’ glance manages to energetically smolder, even though he’s close to dead inside from the film industry’s constant rejection. When spooky butler Max’s (David Thaxton) mug goes up on the big screen, he knocks us over like Nosferatu — albeit a vamp who gets laughs.

And Scherzinger simply stops you in your tracks. With her vocals, too, which give Lloyd Webber’s sweeping ballads pop power.

Her “As If We Never Said Goodbye,” both vulnerable and ravenous, allows the audience to movingly share in her romantic delusion that she’s finally returned to the glamorous spotlight.

And clouds of smoke billow behind her like a dream — hers, Joe’s, ours — as she wallops us with “With One Look” and sings, “I’ll be back where I belong to be!” 

That expressed desire feels a bit like she’s channeling a certain composer. Lloyd Webber has had a rough go lately with the one-two sucker punch of “Bad Cinderella” on Broadway and the awful London revival of “Aspects of Love.” But his long, storied career is a cinematic one of stratospheric ups and difficult downs.

After this “Sunset,” in which his sumptuous score wraps around us like a pashmina, Lloyd Webber can proudly shout, “I’ve come home at last!”