SHERIDAN SMITH bursts into a hushed hotel room, breaking the silence with a warm “Hiya!”, and doling out hugs before tottering to her seat in a figurehugging black dress. The Bafta-winning blonde (who turns out to be wearing a wig, having wet-shaved her head to play a cancer victim in a BBC drama) has star quality in shedloads, but confesses to being extremely nervous about her latest project, a three-part biopic about Cilla Black’s rise to fame.

Cilla charts the Liverpudlian’s ascent from typist and Cavern Club cloakroom attendant to No 1 recording artist and burgeoning TV star, with Smith faithfully recreating her sound (“the soft voice and the big kind of Cilla honk”) and look (via a flame-red bob, false teeth and coloured contact lenses).

“To get to play an icon like that was an honour – scary, but an honour,” the 33-year-old says, bluegrey eyes widening. “Hopefully I’ve done her story justice.”

As a child of the 1980s, Smith’s memories of Black centred on her reuniting families on Surprise Surprise! and asking “our Graham” for a quick recap on Blind Date.

“I’d heard a little bit (of her music), like Alfie. I vaguely remember her having a singing career, but nothing like she actually had,” says Smith.

“She had so many consecutive No 1s, the fact she knew The Beatles, that whole Merseybeat sound that came out of Liverpool in the Sixties, it’s just fascinating.”

In the run-up to filming, the Lincolnshire-born star spent three months researching the singer, filling her phone with Cilla songs and watching old interview clips. And while Smith has the star’s look and voice down to a tee (the false teeth helped her perfect the Scouse accent, she says), she was careful not to attempt a complete impersonation.

“A lot of people mimic Cilla, don’t they? I didn’t want to do her a disservice. There are hints and mannerisms in there, but it’s our version of her.

You become obsessed with whoever you’re playing. I was the same on Mrs Biggs,” the actress adds, referring to her 2012 Bafta-winning role playing Ronnie Biggs’ wife, Charmian.

“You have such a warmth and love for them, I guess, because you admire them so much.”

When it came to meeting the You’re My World singer for dinner, Smith was “very starstruck; kind of babbling on”.

Luckily, Our Cilla was fully supportive. In fact, the Blind Date host has since described Smith’s performance as “absolutely terrific... God knows how she sang so well with those false teeth in”.

“She gave me her number actually, and said I could call her. I was too shy,” Smith recalls, laughing. “You can’t ring Cilla Black every day. I left her in peace and got on with filming.”

The ITV series depicts how Black’s friendship with the Beatles helped her cross paths with manager Brian Epstein (played by Ed Stoppard), and charts her romance with future husband Bobby (Aneurin Barnard).

It also reveals how Black could be ruthless in her ambition – at one point, forbidding Bobby from pursuing a music career, lest it distract him from looking after her own.

“She admitted that she was a tough cookie, but you had to be in the Sixties,” Smith counters. “For her to come out of Liverpool, this little working class girl, and become the star that she was, you’ve got to be ballsy.”

As the daughter of a hard-working country and western duo known as The Daltons, Smith could relate to Black’s background.

“I love that she grafted. I’ve seen my mum and dad graft and bring us up doing all the working men’s clubs every night. In fact, my parents came on set,” she adds. “They were only going to come for two hours; they stayed for two days, they loved looking at all the old instruments, chatting to the guys playing The Beatles.”

Smith might claim to be less determined than Black (“maybe I’m a bit more of a people-pleaser and don’t want to rock the boat”), but her impressive CV suggests that she shares some of her grit.

After performing with the National Youth Music Theatre as a youngster, she moved to London aged 16, and went on to land roles in sitcoms The Royle Family (playing Ralf Little’s girlfriend) and Two Pints Of Lager And A Packet Of Crisps.

Her award-winning turn in Trevor Nunn’s 2011 production of Flare Path brought her to the attention of Dustin Hoffman, who offered her a part in his directorial debut Quartet, alongside Dame Maggie Smith and Billy Connolly.

Since then, she’s had leading roles in ITV’s The Widower (based on the crimes of Scottish killer Malcolm Webster), BBC1’s The 7.39 with David Morrissey and Olivia Colman, about commuters who embark on an affair, and The C-Word, the upcoming drama about real-life cancer blogger Lisa Lynch.

And she’s soon to start filming another threepart series, Black Work, playing a policewoman whose husband is murdered.

“For once, it’s fictional, so there won’t be as much research this time,” she says. “The one thing I’m going to do is go to boot camp, because I’m so unfit. There are a lot of car chases and running on foot – I don’t think policewomen should be getting a stitch like I do.

“It’s totally different again to anything I’ve done,” Smith adds. “I like to keep trying new things, and being a bit of a chameleon.”

  • Cilla, ITV1, Monday, 9pm