The pair kept their tight bond a secret, but Barbara has now cast light on her time with Amy, who died last July, in a new interview with The Mirror.
The actress reveals her husband Scott Mitchell has known the Winehouse family since he was young, and she took the Back to Black hitmaker under her wing when she was battling her addiction issues at a clinic in London.
Barbara said: "I kept our friendship private even though she was often in the news. We kept it a secret. We always said our friendship would be very private because we knew what it would be like (in the headlines)... 'Friends with Barbara Windsor, what's that all about?'
"My husband's family is very friendly with Amy's family. The two have known each other for a long time.
"I live near Regent's Park and she used to go to a clinic near us. She would sit out at the back entrance and have a cigarette. I spotted her one day and said to Scott, 'That's Amy out there having a cigarette, you should go out'. He went out and she said, 'Hello, Scott, I was wondering which house you and Ba lived in'.
"He told her to stop sitting outside and come in. Then, whenever she was there, she knew she didn't have to sit on a wall and could come and see us. She would knock on the door and we would have quality time with her."
Opening up about her memories of Amy, Barbara reveals she used to practice her Peggy Mitchell lines with the singer, who would pretend to be her onscreen rival Pat Evans.
The veteran star added: "There was always an EastEnders script on the coffee table and we would read the scripts together.
"There was one really heavy scene between Peggy and Pat where it really kicked off. I pretended to be Peggy and for the first time Amy played Pat.
"Afterwards she always insisted on playing Peggy, which was lovely. She was very good, she was a very good actress.
"That was one of our smashing moments. It was lovely and we always said we would never tell anyone."
And Barbara admits she was devastated when she heard of her pal's passing at the age of 27: "I was so upset when I heard the news. She was an amazing, amazing talent. It was tragic that she was getting herself sorted out... but that's life, isn't it?
"We stayed away from her funeral but we went to the third Shiva and said prayers with her family."
The 75 year old now serves as a patron for the Amy Winehouse Foundation - and she jumped at the chance to promote the organisation, which was set up by the star's dad, Mitch.
Barbara explains: "Mitch asked me to be patron and I have time now I am not in EastEnders. We raised £25,000 for a children's hospice in Ireland and I have just come back from there.
"It was so moving being there and seeing how much good is done there."
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