Use some quick simple cypher-supposewe say the alphabet backwards, Z for A and so on.

I copied this out carefully in the simple cypher we had agreed on, and handed it to the boy, together with five shillings.

"It's just the simplest cypher in existence," I said.

" Simple cypher, left in hopes that it may yet serve some unfortunate Englishman to escape from the tender mercies of this hole."