This was a very odd one, a client approached me saying that whenever she was typing there was no "Red squiggles" under her mistakes. Assuming the best that maybe it was simply turned off of there was something slightly amiss here I logged on to see the problem myself.
Lo and behold it was true, even clicking check document didn't correct any issues!
So after much head scratching, initially I came accross a document in Microsoft's support assembly that showed Word runs with separate Add-on entities which can sometimes be disabled.
So running with this in mind, I did the following and sorted the problem.
Click the Word Office button
Select the drop down box
Select Disabled Add-in's
Enable the Dictionary spell check!
All sorted :)