"I don't think she would have coped very well with everyone always approaching her to talk, but she was gracious and very lovely, always well-mannered."
Dumbleton says there are scenes in the stories taken straight from incidents she remembers happening at hotels her parents ran. One involves a character riding by on a horse and popping her head through a kitchen window and asking if she could pick apples from a nearby tree; other characters ring equally as true.
"It was a different time and people then were often a lot more colourful. In fact, some of them were as mad as hatters.
"When I read Agatha Christie when I was older — and I think murder mysteries are something you come to later in life — I could understand exactly what she was writing about."
But her personal connection with Dame Agatha, coupled with being able to picture the types of people and places that fill her books, didn't make it any easier for community theatre group Shoreside to get the rights to Towards Zero from the Agatha Christie Trust.
They've spent three years asking if it would be possible to stage the murder mystery but, each time, were knocked back because the play wasn't available to be performed.
"Often they can't be taken to market because someone else has the rights or there's a television or film adaptation soon to come out but we kept on keeping on and then found out in January we could finally have Towards Zero. I was thrilled to bits."
It will be the sixth midwinter Agatha Christie murder mystery put on by Shoreside Theatre; Dumbleton thinks they appeal partly because of the whodunnit aspect but also because there's not a lot of sexual content or swearing.
She says Towards Zero is a little different because it's set at a house party on the perilous Cornish Cliffs where the location of the estate, opposite a village but divided from it by the Fowey Estuary, provides an important alibi for one character. It's meant creating an authentic outdoor setting, complete with grass and rocks.
Towards Zero
July 26-August 4
The PumpHouse Theatre