It's a Playford tune, also called The Twenty Ninth of May.

Random selection from Google comes up wiuth www.eastleighfolkdance.org/MainlyPlayford.pdf for example, which contains the tune, alodn with a lot of other gems "Mostly Playford" as the name says.

It's also in Mike Raven's big book and any other Playfod collection.
Lovely tune! I've been learning it recently.