Accentual Verse

[milo]

I don't understand why Peter's is and Hugh's isn't

First I should point out that it is not a quality judgement as I think peter's is awful (and I told him that when he wrote it)

There are technical definitions that need to be met in alliterative verse, peter's meets them, hugh's doesn't.

Or more simply, ''the repetition of the same initial letter in closely successive words'' Nuttall's Standard Dictionary of the English Language, 1932

That is a definition of alliteration not alliterative verse.