By Stephen Dowling
Jessie Wallace, who plays Kat Moon (nee Slater) in BBC One soap EastEnders, is leaving the show at the end of the year.
Kat and Alfie's on-off relationship hooked the viewers
Wallace, 33, has played the character since 2000, becoming one of the biggest stars of the 20-year-old show.
The bold and brassy Kat, one of the four Slater sisters, is memorably described as "all war paint and short skirts" on the EastEnders website, but deep down is more vulnerable.
Kat was at the centre of one of the series' most dramatic storylines, when she admitted to teenage Zoe Slater she was not in fact her older sister - but her mother.
It was moments like that which made Kat a fan favourite.
The BBC is keeping the details of Kat's departure firmly under wraps, but has promised it will be "explosive".
Wallace, who began her showbusiness career as a make-up artist at the Royal Shakespeare Company, has signed a deal with the BBC that will see her appear in a string of new shows.
It comes at a time when the BBC's flagship soap is seeing a brace of stars departing.
Actress Tracy-Ann Oberman, who plays Queen Vic landlady Chrissie Watts, is leaving the soap, as is Charlotte Avery, who plays Tina Stewart.
And Shane Richie, who plays Kat's husband Alfie, is also leaving the soap.
It also follows the return - and subsequent departure after a scandal involving a webcam - of Leslie Grantham, who played the show's most iconic villain, Dirty Den.
Wallace has played Kat Slater since 2000
And while the show has regularly attracted audience figures of 14 million as recently as January 2004, it is now consistently faring worse than its ITV1 rival Coronation Street.
Radio Times TV writer Jane Rackham says her larger-than-life presence will be sorely missed on the show.
"I think audiences really have loved that 'tart with a heart' persona," she says. "It's never been dull when there's been a Kat Slater storyline. She's been central to some really strong storylines.
"I think Albert Square is going to be a much quieter place without her."
But Ms Rackham says: "EastEnders is much bigger than any of its characters. it carries on regardless, because it's such a major production."
She hopes Wallace finds success out of the soap, but says audiences may find it difficult to divorce the actress from her role.
"Kat was her first major role, and one of the first she ever did. It will be interesting to see what she goes and does now.
"There's been talk of everything up to period dramas - it will be strange to see her in one, trying to be genteel," she says. But she adds Wallace is "raw talent" and is glad the BBC is keeping hold of her for further roles.
In January, EastEnders drew its lowest audience share in more than five years with only 6.8 million viewers tuning in to one episode.
The show had to live without Wallace after the actress took maternity leave from October after giving birth to her daughter Tallulah Lilac.
The soap is trying to reverse falling audiences with a host of new characters and the return of some old favourites - including the Mitchell Brothers Grant and Phil.
Wallace has won six awards for playing Kat Slater
Nicola Methven, the TV editor of the Daily Mirror, says: "I think EastEnders will have seen it coming. They've had time to let it sink in and prepare.
"I think for viewers it will be a shock when Kat and Alfie are no longer there. But there's only so many times a couple like that can get together, and break up, and get together again before they become boring.
"The thing about the Mitchells coming back - even if that's a stunt, it's going to let people get over the hurt of losing Kat and Alfie.
Heat magazine's Julie Emery, a long-time fan of the show, says Wallace's decision to move away while her character is still so popular is a wise one.
"What else can she do - Kat's slept with just about everyone, she's with Alfie - she can't just go on putting on the slap."
She predicts Wallace may bring her many fans to other shows. "I wouldn't be surprised if she become the Beeb's Michelle Collins."