Joanna Lumley has revealed that she suffers from face blindness, which makes it difficult for her to recognise people she knows.
The rare condition, known as prosopagnosia, means you cannot recognise people's faces you've seen before, including those of friends and family.
Speaking recently on the Tracks of My Years podcast, the actor, 77, described living with the condition, explaining that she "kisses everybody" as she can't always tell who she knows or has met before.
"I've got this weird thing with faces, I've got a face blindness, which means I can't tell people from faces," she told host Vernon Kay. "So unless I know who they are, I don't know who they are."
Vernon, 49, explained that he he hadn't heard of the condition, before Lumley pointed out that Stephen Fry has it too.
"This is why I kiss everybody," she continued. "I kissed you today. A, because I wanted to. B, because I actually didn't know whether I knew you or not. I can't tell."
"Sometimes I don't know whether I've seen that person that day or whether I should have seen them."
Lumley went on to add that she kisses so many strangers because she is unsure who people are. "Do I know you, was I married to you, I just don't know?" she concluded.
The Absolutely Fabulous star isn't the only one to have discussed the condition recently. Brad Pitt has also shared his belief that he may suffer from undiagnosed face blindness.
In a recent interview with GQ magazine, the Bullet Train actor, 58, revealed that if he is impacted by the condition it could explain why he struggles to remember people and can come across as “remote and aloof”.
While he has never been formally diagnosed with prosopagnosia, Pitt says he has difficulty remembering new people and recognising their faces, especially in social settings such as parties.
He worries this could lead to people forming the impression that he is "aloof, inaccessible, self-absorbed", and he says he often feels "ashamed" that he can't remember the people he meets.
What is face blindness?
The NHS describes prosopagnosia, or face blindness, as a condition where you cannot recognise people's faces.
Face blindness often affects people from birth and is usually a problem someone has for most or all of their life.
Those living with the condition are often unable to recognise family members, partners or friends, which can have a knock-on effect on their everyday lives.
"A person with prosopagnosia may avoid social interaction and develop social anxiety disorder, an overwhelming fear of social situations," the NHS site explains.
"They may also have difficulty forming relationships or experience problems with their career."
Feelings of depression are also common among those living with the condition.
According to the NHS, there are two types of prosopagnosia: developmental prosopagnosia – where a person has prosopagnosia without having brain damage and acquired prosopagnosia – where a person develops prosopagnosia after brain damage, often following a stroke or head injury.
Several studies have indicated that as many as one in 50 people may have developmental prosopagnosia, which equates to about 1.5 million people in the UK.
While it isn't known exactly what causes developmental prosopagnosia, it is believed it may have a genetic component and run in families.
That's because many people with the condition have reported at least one first-degree relative, such as a parent or sibling (brother or sister), who also has problems recognising faces.
Though prosopagnosia is not related to memory problems, vision loss or learning disabilities, it is sometimes associated with other developmental disorders including autism spectrum disorder.
Treatment for prosopagnosia
While there's no specific treatment for prosopagnosia, researchers are working to investigate what causes the condition, and training programmes are being developed to help improve facial recognition.
Those living with the condition often cope by using alternative strategies to try to recognise people, such as remembering the way they walk or their hairstyle, voice or clothing, but these types of techniques don't always work, particularly if a person with prosopagnosia meets someone they know in an unexpected location or who's changed their appearance.
The Centre for Face Processing Disorders has more information about coping strategies for prosopagnosia.