Actress Carey Mulligan told supporters of the Alzheimer's Society about her grandmother's "heartbreaking" dementia during the charity's Christmas carol service at Southwark Cathedral on Wednesday night.
The Great Gatsby star brought a touch of glamour to the annual festive event but also brought the difficulties of the disease into the spotlight in a moving talk.
"People living with dementia and their families often feel alone and don't have enough support," she said, according to the Daily Mail.
"I'm proud to see the developments in research, but while we power progress for a cure, everyone affected by dementia must have somewhere to turn to for help and advice."
Mulligan, 34, is an ambassador of the Alzheimer's Society. Its carol service this year was dedicated to the memory of her grandmother, who died in 2017 at the age of 91 after suffering from Alzheimer's for 16 years.
She encouraged people who know someone suffering from dementia to reach out and spend time with them.
"Dementia is heart-breaking, but it is possible to live well with dementia. Nan's taught me that," she said.
"This Christmas, if you have a loved one with dementia, spend time with them. Love them, the same way you always have.
"And please, if you can, give a Christmas gift to Alzheimer's Society so we can make sure no one with dementia faces it alone."
Actors Anne-Marie Duff, star of Shameless, and David Bradly, who played Argus Filch in Harry Potter, were also at the service to show their support for Alzheimer's sufferers.
Bradley played a character suffering from dementia in After Life, the Netflix series by comedian Ricky Gervais.
"When you're playing a part, you know it's not real life," he said.
"I can only imaging how devastating dementia is - to learn you have it, to come to terms with it and deal with the impact on families and friends."
He added: "What I do know is that we must do all we can to make sure everyone with dementia has somewhere to turn to after a dementia diagnosis, and fund research into the diseases causing dementia, because it's something we just have to get rid of."
