She has beaten breast cancer twice, been engaged or married to almost every eligible man of a certain age and slapped everyone who crossed her.
But as she loses her battle with terminal cancer, here are some of her most memorable moments.
1. Peggy’s Albert Square return
Initially played by Jo Warne in 1991, the role was recast with Dame Barbara popping up in Albert Square three years later.
During her first episode, Peggy visited son Phil in hospital. “Can’t take my eyes off you, can I? Not for two minutes,” she said.
Dame Barbara immediately made the role her own, banishing memories of the first person to play Peggy.
2. Breast cancer heartache
In 1996, Peggy learned she had breast cancer. It was a storyline handled with sensitivity and acted with aplomb.
The cancer returned in 1999 and Peggy made the decision to have a mastectomy. Hundreds of viewers wrote to the BBC praising Dame Barbara and EastEnders for the way the difficult subject was tackled.
As we now know, Peggy will ultimately lose her battle with cancer.
3. Peggy and Pat: feud and friendship
Barbara Windsor with her EastEnders co-stars including Pam St Clement and the late Mike Reid (Frank Butcher) (John Stillwell/PA)
Peggy and Pat Butcher (played by Pam St Clement) developed into the two leading matriarchs of Albert Square. Their fascinating relationship led to some memorable moments.
In 1998, Peggy and Pat had an explosive confrontation over Pat’s long-time love Frank Butcher (the late Mike Reid). Glasses were thrown and insults were hurled with venom.
“You bitch!” cried Pat as she slapped Peggy.
“You cow!” Peggy responded with a slap.
By 2000, Peggy had wed Frank and Pat was married to Roy Evans. However, Pat and Frank had been having an affair.
The two lovebirds had planned to run off together, but Peggy found out and humiliated the couple in front of everyone in the Queen Vic by reading Frank’s letter aloud.
“One thing I’ve learned since I’ve been married to Mr Butcher is never underestimate his capacity to make a cock-up of things!” she cried before slapping both Frank and Pat.
Years later in 2008, Frank’s former wives came to blows after learning of his death.
“Get outta mah pub!” Peggy screamed at Pat as they rowed over which of them he had loved more.
“You bitch!” cried Peggy as she slapped Pat.
“You cow!” Pat responded, slapping her in return.
In 2009, Pat and Peggy found a bottle of vodka inside an ice-cream van. They polished it off, got tipsy and ended up declaring their love for one another.
4. Peggy meets Boris
In one of the more bizarre EastEnders cameos, Boris Johnson, the Mayor of London, visited Walford and had a run-in with the fiery landlady.
Dame Barbara Windsor with Boris Johnson (BBC)
“I do so admire a man who devotes his life to serving society. I nearly went into politics myself you know,” Peggy told him.
5. Peggy versus Chrissie
Peggy’s daughter Sam (Kim Medcalf) had been framed for the murder of Den Watts (Leslie Grantham) by his wife Chrissie (Tracy-Ann Oberman).
When Peggy discovered the truth, she stormed to the graveside and screamed: “Chrissie Watts! Murderer!”
Like an avenging angel, she lunged at Chrissie and pushed the woman into her husband’s grave.
“Tell Den you’re sorry! Tell Den!” Peggy screeched.
6. Peggy slaps Phil
In 2010, matters came to a head over Phil’s substance addiction. Peggy confronted her son, who told her she had pushed all her children away with her nagging.
Steve McFadden as Phil Mitchell in EastEnders (BBC)
Peggy slapped Phil. He threw her out and told her she is nothing.
7. Peggy exits
In 2010, a crack-crazed Phil torched the Queen Vic. Luckily, Peggy escaped. However, she took stock of her life and decided to leave Albert Square.
Peggy could not persuade Phil to go with her. “Go back inside, love. Go on, I’ll be fine. Go on, darling, go back inside,” she told him and walked away.
8. Peggy breaks her silence with bad news
Peggy’s surprise appearance in the episode broadcast on January 15 was tinged with sadness. After a long silence, she told Phil that her cancer has returned and that she is dying.
Peggy’s final appearance in EastEnders will be broadcast at 7.25pm on BBC One.