Cats revival: Timeless appeal or is Nicole Scherzinger the reason for its success?

Something improbable – one might even say downright unlikely – has happened in the West End this past month. Cats, the long-running Andrew Lloyd Webber behemoth, which bowed out of the capital more than a decade ago for the simple reason that everyone in the capital had seen it, has been granted yet another life.

It was brought back to fill the Palladium in December when the Harry Hill pastiche I Can't Sing! – more brouhaha, ultimately, than ha ha – tanked, then closed, leaving the place empty. Acting swiftly, Lloyd Webber reassembled the original production team – director Trevor Nunn, costume designer John Napier, choreographer Gillian Lynne – to reignite a Cats 2.0 – which, in point of fact, has not really been updated at all save for a newly penned "rap" for the character Rum Tum Tugger, transforming him from rakish tomcat to urban bad boy. Otherwise, it's the same as it ever was.

The hasty revival instantly paid off, proving a hit with audiences and critics alike, and is now booking all the way up to spring.

In truth, Cats had never really gone away, but was rather merely relegated to rep in seeming perpetuity. To bring it back to London with fanfare, Lloyd Webber required a star attraction for Grizabella, the role made famous in the original by Elaine Paige. Grizabella is by no means a lead role in what is strictly an ensemble piece, but the character does get to sing the show's most famous song, "Memory", which casts all else in shadow. And so he drafted in the face of Müller yoghurt, Nicole Scherzinger. This former Pussycat Doll and X Factor judge had recently released an album, Big Fat Lie, that failed to light up the charts as a woman with her rapacious ambition might have expected, and so the prospect of West End reinvention understandably appealed.

The American has impressed. "A drop-dead stunning presence," said The Independent in December. And so the show that debuted in New York on 7 October 1981, and which has since been seen by more than 70 million people in 300 cities, and staged in London alone almost 9,000 times, is back back back, an all-singing, all-dancing, slightly camp, post-recession-busting sensation.

Which rather begs the question: how? How has a show featuring fully grown thespians dressed in leggings and faux fur become one of the most successful and enduring musicals in the genre's history? And when its current lead slinks off into the sunset, will Cats keep its claws in its audience?

According to the creator himself (Lloyd Webber, not God; but easily confused), the secret is a simple one: people like cats. Quite true, of course. On the other hand, people like dogs, too, yet there are currently no West End hits to reflect this. Kerry Ellis, who comes into the production as Nicole Sherzinger departs, says: "If we knew what made a theatrical hit, we'd all be millionaires, but it is simply one of the enduring classics, and features some of Andrew's very best songs."

Cats is far from your typical musical. It is light on narrative, for starters – a bunch of strays with names such as Carbucketty and Old Deuteronomy congregate in a junkyard and sing self-congratulatory songs about themselves – but then its source material, T S Eliot's Old Possum's Book of Practical Cats, was merely a series of poems parents might have liked to read to their children when it was published in 1939. It takes me, not an affiliate of any of the production's many unofficial fan clubs, about 15 minutes to realise that I don't really need to know what is going on here because nothing much is going on. It's all just razzle and dazzle, and a lot of admittedly terrific dance routines. You'd have to work conspicuously hard not to enjoy it.

"Cats appeals to all ages, and has always been great for the tourist market," says Mark Shenton, theatre critic for The Stage magazine, "because you don't need to speak the language to understand it. The lack of plot makes it undemanding, and the whole spectacle is really sort of exhilarating."

Shenton points out that it was one of the first truly immersive theatrical experiences when it opened. At its original home in the UK, the New London Theatre, the stage revolved, making audiences feel part of the show. But what once seemed novel is now essentially a period piece, a little dated, he says, and saturated in its own nostalgia. So why do the hordes still flock nightly?

"Well, it's endlessly renewable, I suppose, because a new generation hasn't seen it yet. They have their chance now."

It is a cold and crisp January evening, 90 minutes before showtime, and five weeks into its resurrected run. A sudden blaring of the fire alarm – a drill, we are assured – prompts a rush of activity backstage, and so various crew and two dozen cast members, many of whom are still only half made up and partially costumed, spill out on to the street. There are all manner of unexpected sights on any given day in Soho, but one is rarely afforded the spectacle of quite so many jobbing actors congregating en masse like this. Commuting office workers openly gawp.

"Look!" says one passer-by, adding, with a piercing accuracy: "Cats."

Fire drill over, the rehearsal resumes in earnest, and then it's down through the warren-like corridors that comprise the Palladium's intestines to respective dressing rooms, where the actors put the finishing touches to their makeup with the practised skill of professional face painters. Charlene Ford is one of them. She tells me that she had been in the touring production for a year before joining its London revival. She is 29, and as Bombalurina has graced stages in Italy, Israel and, more recently, Torquay. It is, she explains, a very demanding show.

"Physically, it takes its toll. Even if you are off sick or injured for just a couple of days, your stamina can drop. I'm definitely brighter on Monday and Tuesday nights," she adds. "By Saturday, I'm ready for a drink in the pub afterwards…"

Next to her, smiling broadly (and bright orange, with whiskers), is Zizi Strallen, an actress with more connection to the show than most. "I'm the fifth member of my family to be in it," the 24-year-old says. Her aunt, Bonnie Langford, was in the original cast; her parents have also been in it, likewise an older sister. "It's in our blood, you might say." Consequently, when her mother came to see her on opening night, "it was all very emotional". Strallen has played the scampish Demeter almost every night for the past eight months. "My father wanted me to become a lawyer, you know," she says.

Front of house, there is brisk trade in the family-sized bags of Maltesers, and the cloud that hovers above everyone has a distinct tang of perfume, redolent of the fact that the crowd, tonight at least, is predominantly female. Lloyd Webber's assertion that the people who love Cats are predominantly cat lovers is borne out by the fact that several cat charities advertise in the production's official programme. Later, I contact one, the Mayhew Animal Home, and it tells me that since the musical's return to the West End, it has seen a 14 per cent increase in donations.

As people find their seats, the talk that I overhear revolves primarily around Grizabella, and Nicole Sherzinger; "that one off X Factor," as someone puts it. As this is Sherzinger's last week, Ellis, a 35-year-old musical theatre pro, will be taking over from Monday.

"And I'm terribly nervous about it," she tells me when we speak the following day, "but in a good way, I hope! There is so much expectation, so much pressure." I ask why, given that Grizabella occupies just 10 minutes of stage time. "Because everybody is waiting for the song, of course. For 'Memory'."

She's right. Anticipation for it hangs over the show like Christmas Day does throughout the month of December. "We get to hear it twice," a woman next to me in row M whispers. "Before the interval, and after!"

Despite the song spawning scores of cover versions – 150 at the last count, by a crew as motley as Barry Manilow, Barbra Streisand, and even Liberace – "Memory" remains Elaine Paige's. It was Paige who sang it first and, according to The Stage's Mark Shenton, sang it definitively.

"For my money, Nicole Sherzinger's is the X Factor version. It doesn't have to be done as a big torch ballad."

In Elaine Paige's throat, "Memory" possesses the purity of a whispered hymn; in Sherzinger's, it is huge and vast, and she delivers it with an untrammelled gusto. As Shenton concedes, "People do seem to like her." They do. When Sherzinger hits the high notes, I rather suspect that every hair on every neck rises to attention.

There is nowhere, really, the show can go after "Memory" and so, shortly after, it finishes. Half the audience offer a standing ovation, but this will not do for Sherzinger, it will not do at all, and she goads the rest of us to our feet until the applause is loud enough, and long enough, to satisfy.

Freedom beckons now: fresh air, e-cigarettes, gossip. I fall into step with a trio of middle-aged ladies drifting towards Oxford Street. "Loved it," one says. "Really wonderful. And bloody hell, that Pussycat Doll can't half give it some welly, can she? I never really rated her before, to be honest. I do now."

Cats is at the Palladium Theatre, London, until 25 April