Van Morrison’s signature tune. And the only song of him I know (sorry for my ignorance).
But you can find it on almost any „Greatest / Best / Most Influental / etc. Songs of all Times“ list.
Four parts [ A ] intro, [ B ] verse ,[ C ] chorus and [ D ] sha-la-la-la
Not straight fingerstyle, add some strums ad lib. The double-stop fills are a little tricky.