I have a most interesting book entitled Richard Taylor: Missionary Tramper, published by A.H. and A.W.
Reed, written in 1966 by A.D. Mead who also wrote Wanganui River (1957). I quote from his introduction, “One source
of variation was due to dialect; in particular the aspirate h, whether by itself or in the
combination wh, was fully sounded
only among the Ngapuhis of North Auckland; further south it was either lightly
sounded or almost suppressed…”
I see four reasons not
to change “Wanganui” to “Whanganui”.
