Why does this MWE not use correct UK English hyphenation? The second line has an influence on alternate, but not on nevertheless:
\documentclass{article}
\usepackage[UKenglish]{babel}
\begin{document}
\fbox{\parbox{8mm}{\hskip0pt alternate}}
\fbox{\parbox{8mm}{\hskip0pt nevertheless}}
\end{document}
Correct hyphenations are:
BE: never|the|less (Oxford)
AE: nev·er·the·less (Merriam-Webster, Oxford)
(Bonus question: Why is the first word in my MWE not hyphenated? Answered.)
Some part of my log output:
This is pdfTeX, Version 3.14159265-2.6-1.40.17 (MiKTeX 2.9 64-bit) (preloaded format=pdflatex 2016.6.30) 19 JUL 2016 13:13
entering extended mode
**./hindex.tex
(hindex.tex
LaTeX2e <2016/03/31> patch level 1
Babel <3.9r> and hyphenation patterns for 4 language(s) loaded.
This output is exactly the same, regardless of whether I use english or UKenglish.

alternateis (incorrectly) different from the AE hyphenation; and the BE hyphenation ofneverthelessis (incorrectly) identical to the AE hyphenation. Looks like a duplicate then, the other question's answers answer this question pretty well. – bers Jul 19 '16 at 17:34