Here's something interesting: In 1926, Archie Christie, Agatha's first husband, asked her for a divorce, as he was in love with someone else. She disappeared. For three weeks. "The missing mystery writer." I'm sure people were starting to think she'd been murdered. She was found at a small hotel and told the police that she was missing the memory of those last three weeks. There's a movie, Agatha (1979), about it.
The best time to plan a book is while you're doing the dishes.
I don't think necessity is the mother of invention. Invention, in my opinion, arises directly from idleness, possibly also from laziness - to save oneself trouble.
It is a curious thought, but it is only when you see people looking ridiculous that you realize just how much you love them.
There is nothing more thrilling in this world, I think, than having a child that is yours, and yet is mysteriously a stranger.