Searching for crime book

[user79]

Hi all, 

 

I have searched and searched online but can’t find this book, so hoping one of you might have the answer! 
 

I’m thinking of a crime novel, where one of the clues is that something is hidden between two pages, but this proves to be impossible as the pages would have been back to back because of the page numbers. It’s an older novel (pre 1990). Potentially Dorothy L Sayers but I can’t remember the title or author or setting. 
 

Any ideas? Thank you SO much. 

[France]

I think I've read all of Dorothy L Sayers and don't remember any clues like that.

 

Can you narrow the time period down a bit? 

[user79]

That’s helpful to rule her out - thank you! All I know is that the book was read in about 1975 so must be written before that. And it was Agatha Christie / Sayers / Conan Doyle era. Thanks for your help!