The 82-year-old actress suffers from Alzheimer's disease and though her day-to-day memory isn't very good, her friend Christopher Biggins revealed she is "great on the past" and even remembers many of her lines from the nine 'Carry On' films she appeared in between 1964 and 1974.
He told Best magazine: "I had lunch with Barbara recently. She's fantastic. We laugh a lot, she's great on the past too.
"She can remember all her 'Carry On' jokes and also songs from the old time music hall. The other day, she sang 'The Boy I Love Is Up In The Gallery'.
"[Her memory] is not so good when she tries to remember things from day to day."
Barbara's husband Scott Mitchell - who cares for her at their home - recently said that she's still got a sense of humour.
He said: "The thing that we know about dementia and Alzheimer's is that it's a progressive illness, so you know you're heading in one direction. So, yes, things progress but she still has that wonderful sense of humour, she can still laugh and have a giggle and watch telly, and we go out occasionally.
"Whenever we get an invitation what I say is let's say yes but I will let you know on the day if we're going to be there or not, and it's totally dependent on how Barbara is.
"We have the odd days out, we went to Downing Street and she was shouting at all the photographers and told them to behave themselves.
"Music helps, that's a very common thing. That's the thing about music and dementia it triggers the brain."