A representative for actor Steve McFadden, who plays Dame Barbara’s on-screen son Phil Mitchell, said he was “devastated” by her death.
Dame Barbara was diagnosed with the disease in 2014 and had moved to a care home earlier this year.
She appeared in nine films in the Carry On comedy series, plus Sparrows Can’t Sing, for which she was nominated for a Bafta, as well as parts in Chitty Chitty Bang Bang and On the Fiddle with Sir Sean Connery.
She was well-known to millions of TV viewers for her portrayal of landlady Peggy Mitchell in EastEnders, starring alongside her on-screen children Ross Kemp and Steve McFadden.
Her last appearance in the soap came in 2016, the same year she was made a dame for her services to charity and entertainment.
She also worked in theatre – making her stage debut at 13 – and appeared in productions including Oh! What A Lovely War and Fings Ain’t Wot They Used To Be.
After her dementia diagnosis, Dame Barbara became an ambassador for the Alzheimer’s Society and met Mr Johnson to raise awareness about the disease.
The star delivered a letter signed by 100,000 people pleading for better care for people affected by dementia and saying the system was “completely inadequate, unfair, unsustainable and in dire need of more money”.
Mr Mitchell, who campaigned alongside his wife, said of her death: “It was not the ending that Barbara or anyone else living with this very cruel disease deserve.
“I will always be immensely proud of Barbara’s courage, dignity and generosity dealing with her own illness and still trying to help others by raising awareness for as long as she could.”
The couple went public with her diagnosis in 2018 and Mr Mitchell had said they had been “really nervous” about revealing she was affected by the condition.
In his statement he thanked the public, family and friends for support which he said “Barbara deeply appreciated”.
He added: “I’ve lost my wife, my best friend and soul mate and my heart or life will never feel the same without you.”
The Alzheimer’s Society said it was “incredibly grateful” to Dame Barbara and her husband for their work bringing awareness to the disease.
In a statement, the charity said: “Dame Barbara Windsor was an amazingly true, much-loved national treasure, and in speaking out about her experiences shone like a beacon for others affected by dementia.”
Like her EastEnders character, Dame Barbara was born in east London, in Shoreditch in 1937.
The actress married Mr Mitchell in 2000, with the pair having first met in 1992.
If you, or someone you know, has been affected by dementia you can find more information and support here.
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