For a change: How to Set the Proofing Language in MSWord

Q. Sometimes I open files that have either been sent from the USA or have been created using the US English version of MSWord.
As a result, when I want to spell-check this document the Spelling Checker 'invokes' the US English Dictionary, which slows me down as it stops at every UK English word (Examples: Colour, Colourised or Traveling).
Is there a way to force MSWord to always pull up the UK English Dictionary?
I looked into Preferences but couldn't find it in General, Proofing, Language nor Advanced.

A. I found the solution in MSWord Help:
1. From the "Review Menu", choose "Proofing Language..." and a Dialogue Box will appear: "Language".
2. Click on "√ABC English (United Kingdom)",
3. Click on "Set as Default",
4. Click on "OK".
However, although the change took effect onscreen, i.e. it now shows "English (United Kingdom)" as the "Default Language" in the "Language" Dialogue Box, "English (United States)" still showed up in the Spelling Checker Sidebar (all the way at the bottom), when I pressed F7.

5. So I opened the "Language Preferences..." Dialogue Box ("Review"->"Language"->) and selected "English (United States)" to be added to the list of editing languages.
6. When I pressed the Add Button, a message appeared: "Please restart Office so that your language changes can take effect.".
7. I did so and when I restarted MSWord, "English (United States)" was still the "Proofing Language".

I repeated steps 5. to 7., only now I pressed "Remove" after selecting "English (United States)" in the list of installed Editing Languages.

I then repeated steps 1. to 4. and now it works like a song!