Can anyone tell me the name of a novel I read years ago that involved diamond smuggling. Key character was an old woman who baked the diamonds inside a loaf of bread. Can't remember who wrote it, sounds vaguely Graham Greeney but I don't think it is.

Is it The Comforters - Muriel Spark?

Ha, yes, I think you're right! I have a copy on my bookshelves, and it appears to be the one. Muriel Spark was lurking at the back of my mind, should have just gone and checked through them. Well done, Chris, thank you.