Actor Timothy West told how his wife, Fawlty Towers star Prunella Scales, has "a sort of mild Alzheimer's".
West, 79, talks about Scales' condition in a new More4 documentary, Grand Canal Journeys.
The actress, now 81, is best known for her role as Basil Fawlty's wife Sybil in the classic comedy, but has continued to notch up screen roles.
West, who last year appeared in Coronation Street and has since joined EastEnders, tells the programme, which is broadcast later this month, that Scales suffers from "a sort of mild Alzheimer's", according to the Radio Times.
The couple have been navigating Britain's canals on a slow boat ever since they first sparked a passion for the hobby when they borrowed a friend's boat for a fortnight in the 1970s.
And West tells the programme, in which the pair embark on four canal journeys across Britain, that the journeys are perfect for his wife because of the difficulties with her memory:
She can't remember things very well, but you don't have to remember things on the canal.
You can just enjoy things as they happen - so it's perfect for her."
Scales says that she was determined not to let the condition keep her from the stage.
"I always say I want to die on the eighth curtain call," she says. "Eight will mean the show's been rather a success. I just hope I'm somewhere near the middle and have been reasonably good in the part."