Peggy first appears in EastEnders when Sam's desire to escape from her family causes her to elope with Ricky Butcher at the age of sixteen. Peggy attempts to stop them marrying, but is unsuccessful. Peggy is then absent for a period of three years, during which time her relationship with Kevin ends.
She returns to Walford in November 1994 when her sons fall out, after Phil has an affair with Grant's wife Sharon Mitchell. Peggy becomes acting landlady of The Queen Victoria public house. Blaming Sharon for the affair, Peggy tries to force her out of Walford, resulting in Sharon signing over her share of the pub and leaving the Mitchell family as the sole owners, with Peggy in charge. Peggy enters into a relationship with businessman George Palmer, unaware that he is a criminal involved in illegal money laundering. She instigates a hate campaign against local resident Mark Fowler when she discovers he is HIV positive, beginning a feud with his mother Pauline Fowler. Peggy later recants on her position when she is diagnosed with breast cancer. She initially refuses surgery and breaks up with George, fearing that he will not be able to handle her illness; however, with the support of her family and assurances from George, she eventually goes through with a lumpectomy. Peggy and George become engaged, but their relationship ends when Phil reveals his criminal nature.
Peggy goes on to begin a relationship with local car lot owner Frank Butcher, and they become engaged. Peggy has doubts about the wedding when her cancer returns and she has to undergo a mastectomy, however she ultimately decides to go through with it. Tension develops between Peggy and Phil when Grant leaves for Rio de Janeiro after a violent fight with his brother. To spite Peggy, Phil sells Grant's share in the pub to local businessman Dan Sullivan for £5. Peggy loathes Dan, and the two frequently row over the running of the pub. Also, Dan had stolen Frank's son Ricky Butchers wife Bianca Butcher off Ricky by having an affair with her. Dan revels in winding Peggy up and insulting the Butchers. He even stitches Phil up and Phil later finds out. Eventually, Peggy and Phil call a truce, and are able to force Dan out of Walford when Phil wins the pub back off Dan in a game of poker. Peggy discovers Frank is planning on leaving her for his ex-wife Pat Evans, so shames them by reading Frank's Dear Jane letter to the entire pub, and then slaps them both in front of everyone. She throws Frank out, and he leaves Walford without Pat.
Still recovering from Franks departure, Peggy becomes depressed and begins to rely heavily on tranquillisers. When Frank's daughter Janine Butcher taunts her on Christmas Day about her father finding love with a new woman, Peggy begins drinking heavily and smashes up the pub with a baseball bat. The next year, Peggy is forced to sell the pub, having been left in debt by Frank, and is furious to discover the new owner is Sharon. Peggy begins dating Harry Slater, who owns a bar in Spain and convinces her to move there with him. They become engaged, but break up when it is revealed that Harry is guilty of sexually abusing his niece Kat Moon. When Phil begins dating Sharon again and becomes joint owner of The Queen Victoria, Peggy moves back in. She later becomes sole licensee again, when Sharon sells her half of the pub back to her.
Peggy is then briefly reunited with Frank when she travels to Spain to attend his funeral. She discovers he is still alive, and has faked his own death to avoid debtors. Peggy decides to move to Brazil to be with Grant, and departs from the series for two years, returning briefly to attend her daughter Sam's wedding to local businessman Andy Hunter.
When Peggy returns to Walford in 2005, she is furious to discover Sam has lost possession of The Queen Victoria, and that the new licensee Chrissie Watts has framed Sam for her husband Den's murder. While trying to exonerate Sam and reclaim ownership of the pub, Peggy ignites a feud with Johnny Allen, who also wishes to buy The Queen Victoria. Johnny hires a mobster to assault Peggy, but she is saved by her sons, Phil and Grant. They are able to deal with Johnny, secure Sam's release from prison, and return Peggy to The Queen Victoria. Peggy begins a romance with Jack Edwards, the father-in-law of Peggy's first cousin once removed-in law Billy Mitchell. However, when Peggy discovers Billy's newborn daughter has Down's syndrome, she declares that the baby should be put up for adoption, causing friction in her relationship with Jack. Although Peggy comes to accept the baby, Jack breaks up with her and leaves Walford.
Peggy starts a relationship with her brother-in-law, Archie Mitchell, father of Ronnie Mitchell and Roxy Mitchell. They get engaged and Archie begins subtly controlling Peggy. They marry, but it ends a few hours later, when it is revealed that Archie lied to Ronnie about her infant daughter's death. Peggy has Archie evicted from The Queen Victoria, and tries unsuccessfully to coerce Phil into murdering him. Archie leaves Walford, but later returns. Peggy files for divorce, and Archie plots revenge on the entire Mitchell family.
When Peggy loses the bail surety she has paid on behalf of her daughter Sam (who breaks the conditions of her bail following coercion from Archie), the Mitchells are forced to use The Queen Victoria to gain a collateral Loan from Ian Beale. Archie blackmails Ian to sell the loan to him, and when the Mitchells are unable to meet the loan repayment, Archie evicts them and assumes ownership of the pub. However, Archie is murdered on Christmas Day 2009 by an unknown assailant. Peggy grieves for Archie, but she and various other members of her family become suspects for Archie's murder. Following a police enquiry, Bradley Branning is posthumously found guilty of the murder, though unbeknown to everyone else, the actual murderer is Stacey Slater. In his will, Archie leaves The Queen Victoria to Roxy. Roxy superannuates Peggy, until Archie's estranged son Danny Mitchell manipulates Roxy into reinstating her.
After being disgusted with the state of the Square and learning that a councillor has stood down, Peggy and Pat both decide to run for council and are interviewed by journalist Harvey Freeman. Eventually they both pull out of the election, but Harvey hears of this and individually invites them both out for drinks. They soon discover that Harvey has been seeing them both in secret and end their respective relationships. However, Peggy stays in touch with Harvey, not knowing that Pat is as well. They both finally discover his two-timing ways again, and humiliate him in punishment. Celebrating their friendship, Peggy and Pat go on holiday together. When Peggy returns, she is annoyed to learn that Ronnie and Roxy's mother Glenda Mitchell is back. Peggy and Glenda attempt to outdo each other in order to win Ronnie and Roxy's affections, and trade insults several times. When Peggy hears that Archie raped Ronnie when she was 13 years old, she refuses to believe it. Roxy tries to get Peggy to listen to Ronnie but she refuses so Roxy decides to move out, leaving Peggy on her own. Peggy then invites Pat to move in with her, and the two attempt to stop Roxy from selling the pub.
Peggy's grandson Ben faces a prison term for grievous bodily harm. To avoid this, Phil plans to flee with Ben and his family abroad. Peggy talks Phil out of it, saying that Ben can cope with 6 weeks in jail. However Ben is subsequently sentenced to 10 months. Soon after, Phil's daughter Louise Mitchell asks Peggy when she will see her mother Lisa Fowler again. Peggy reveals that Lisa wants to see Louise, but she insults Lisa so Louise runs away. Phil insists that Peggy does not get the police involved, but she does anyway. Once Louise is found, Phil confronts Peggy, saying she should not have told Louise about Lisa or called the police. Peggy says Louise would be better off without Phil, and that sometimes she thinks Phil is unfit to be a parent. Phil responds by slapping his mother and leaving her bruised. Peggy then sneaks Louise out of Phil's home, and takes her to Lisa's house. There, Lisa asks Peggy if she can assure her that Phil will never harm Louise. Peggy cannot, and decides to let Louise stay with her mother permanently, as long as Phil can visit her. However, when an angry Phil goes to Lisa's house to retrieve Louise, he finds that they have left. Phil gets drunk, and publicly blames Peggy for losing him both of his children.
Peggy meets Ken Tate, a brewery representative interested in buying the pub. She starts to like him and invites him to a barbecue. Afterwards, she tells Ken she hopes the brewery will employ her as the landlady but he says they want to make changes and would bring in someone younger. However, Roxy eventually realises that Peggy is the best person to run the pub and signs it over to her. At the reopening of the R&R nightclub, Peggy and Glenda argue, and Peggy realises that Glenda knew that Archie was abusing Ronnie. She reveals this to Ronnie, who rejects her mother. Peggy arranges a family dinner to help Ronnie feel better, and invites her sister Sal, but Sal insults all of Peggy's children and grandchildren, so Peggy orders her out. She then goes to find Phil to say they can be a family, but finds him on the floor, high on drugs. She offers to help him but he insults her and she slaps him, so he throws her out. Peggy then decides to try and make amends with Sam. She secures a visit but Sam tells her she is dead to her and when she stands up to leave, Peggy sees that she is pregnant. Peggy asks Minty Peterson to convince Sam to allow Peggy to see her, but when he returns, he tells Peggy that Sam will not see her and will not try again because of how Peggy and Phil treated Sam and she is not fit to be a mother. Peggy then looks at Sam's old baby clothes in tears. Meanwhile, Phil goes missing.
Peggy had became quite close to her two nieces (later stepdaughters) Ronnie and Roxy. At first, she asked them to leave because The Mitchells where still trying to deal with the fallout of Stella's death. But they offered to stay the Vic for Peggy whilst she, Phil and Ben went off to visit Grant. When Peggy returned, she asked the girls to stay in Walford for good. with Peggy sometimes referring to them as "her girls"
Relations were strained for the three Mitchell women by the arrival of Ronnie and Roxys father Archie persuaded Peggy to marry him and he moved into the Vic. Ronnie, who hated her father. was eventually forced out when Peggy chose Archie over her. Peggy and Ronnie's relationship was utterly destroyed by Archie's meddling, even though they both deeply cared for one another.
After Archie's evil schemes forced him out of the Mitchell family, Peggy tried to make amends with Ronnie. Ronnie moved back into the pub and things went back to normal.
Following Archie's death, he left Roxy the Queen Vic. which he had managed to steal from Peggy. Roy being the new landlady of Peggy's beloved pub almost costed Peggy and Roxy there relationship. With Roxy forcing Peggy out of the pub so that she could bring new bartenders in. Peggy schemed with Roxy's brother Danny to steal the pub from under her nose. however, Realising she couldn't fleece her surrogate daughter. Peggy had a change of heart and Danny was disowned.
In the months leading up to her departure, Peggy and Roxy managed to solve there differences when Roxy discovered the only person to run the Vic is Peggy. however, the interference of Ronnie and Roxys biological mother Glenda threatened to cause a rift between Peggy and both of the girls
Peggy and Glenda first met when they where dating brothers Eric and Archie Mitchell. Glenda knew that Peggy was the women Archie really wanted and began to resent Peggy for this. Eric married Peggy and Archie married Glenda, but he would spend the next 10 years of there married life making her suffer because he couldn't get his dream girl.
When Glenda returned to Walford after Archie's death, Peggy thought Glenda was neglectful and tried to force her out of the Mitchell family.
When Sam goes into labour, she asks for Peggy, and Sam gives birth to a baby boy, but says she wants him adopted. Peggy convinces Sam to keep the baby by telling her it will be the only way to get back with her ex-husband Ricky. Sam's prison sentence ends and she returns to The Queen Victoria. Billy tells Peggy he has found Phil and takes her to an estate. Peggy wakes Phil and tells him to come home as Sam has had a baby but he says he does not care and that she made him this way. She tells him if she had a gun she would tell him to shoot himself as he would be better off dead, and leaves in tears. Peggy's name goes back above the door of The Queen Victoria and she decides to let people know by throwing a wedding reception for Janine and Ryan Malloy. She goes to Janine's hen party at R&R where she argues with Janine and Pat, so she walks out. Dot Branning tells her that Phil is acting the way he is because of the drugs, so Peggy asks Billy and Minty to close the pub and help her bring Phil home, which they do, locking him in the upstairs living room with the windows and door boarded shut. At the wedding reception, Stacey hears Phil and believes it is Archie, still alive, and tells Peggy. Peggy assures her that Archie is dead as Bradley killed him, but Stacey reveals that she did, leaving Peggy shocked and angry. Peggy calls the police but is stopped when a drunken Phil comes down the stairs. He tells her she took away his children, the things he loved most, so says he will take away the one thing she loves the most – the pub. He lights a match, throws it down and the fire spreads quickly. After refusing to leave, Peggy is forced outside but realises Phil is still inside. She and Billy rescue him, and Peggy watches in horror as the pub is destroyed.
The next day Peggy realises Phil was right, that she had put the pub before him, making him the way he is. She tries to blackmail Stacey into taking the blame for starting the pub fire but Stacey asks her to think of her daughter Lily and Peggy relents. She decides to leave Walford and take Phil with her as she believes he needs her. However, he tells her she needs him but suffocates him. She then decides to leave on her own despite Phil and Sam begging her to stay. After saying tearful goodbyes to all her family and making peace with Phil, Peggy takes one last look at The Queen Victoria and leaves Albert Square.
Peggy returned to EastEnders for a guest stint in September 2013. Carl White had purposely crashed a car with Phil in it, leaving him severely injured and hospitalised. Peggy visited Phil at Walford General Hospital and warned him to not let Carl walk over him. Peggy reminded Phil that he mustn't let Carl take control of his businesses. Shortly after Peggy left the hospital and made a short visit to Albert Square to say a final goodbye to Pat (who had died two years previously), leaving a bottle of alcohol on Bianca's doorstep (Pat's previous home) as they never had the chance to have a final drink due to Peggy's sudden departure three years earlier.
Peggy made another guest appearance in EastEnders in September 2014, this time, however, Peggy's scenes were set in Spain. As Phil and Sharon's wedding day looms, Peggy told Ronnie she doesn't want to attend but instead told Ronnie and Aunt Sal to go and make sure they stop the wedding. However, they fail to stop the wedding and Phil and Sharon marry.
Peggy returns to Albert Square in February 2015 to speak to Dot since her son, Nick, had cut the breaks on Roxy's car, committed Ronnie and set up Phil. Dot confided in Peggy and admitted to her that Nick had died. Before leaving, Peggy made a visit to her beloved pub, the Queen Vic, and asked for a drink - although the Vic was shut. Peggy and the new landlord, Mick Carter, had a disagreement and he asked her to leave, mirroring her iconic words "Get outta' ma pub!".
The character returned in January 2016 where it was revealed she had cancer again. In May 2016 she came back to Walford and said that her cancer was advancing, it had spread to her bones and her brain. She started getting hallucinations of the ghost of her frenemy Pat Evans and even spoke to her ghost. Peggy said she wanted to die like a queen rather than become a vegetable so she overdosed on tablets and died in her sleep. She was 74.
Phil is devastated to find her body, and a letter from her urges him to love himself as others love him. Peggy's funeral takes place on 4 July 2016. Phil is due to give a eulogy to her there, but gets too emotional and runs home. Sharon later calms him down by revealing that Peggy was the one who sent Eric to prison when Phil was a child, not corrupt police officers as he was previously told, and that she did it to protect him. Phil later works up the courage to finish his eulogy to Peggy at the wake, and then returns to her grave at the church to finish his goodbyes to her, unaware that Grant has secretly left a rose at the grave.
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