Thanks Thierry, that indeed was the problem.
I am not sure who to advise to correct the documentation in Writing R
Extensions though because I was following the instructions there:
"... the encoding may be declared using a comment like
%!\VignetteEncoding{UTF-8}
If the encoding is UTF-8, this
Dear David,
Have you tried removing the exclamation mark in %!\VignetteEncoding{UTF-8}?
I think it should be %\VignetteEncoding{UTF-8}
Best regards,
ir. Thierry Onkelinx
Instituut voor natuur- en bosonderzoek / Research Institute for Nature and
Forest
team Biometrie & Kwaliteitszorg / team Biome