Donald Davie's Some Notes on Rhythm in Verse
It is a short piece comprising seven numbered paragraphs. He makes a case for scansion being 'a sort of crutch or scaffolding in the act of composition'.
The first paragraph states that the boundary between free verse and metred verse is 'smudged'. He writes: "If you shorten an iambic measure to the trimeter, and then allow yourself all the liberties that traditional prosody allows you, you have a measure which few readers will scan, even subconsciously."