Change the en dictionary for the RAD Editor form EN

When you are opening the RTE editor the current item language name is transferred there as the “la=xx-XX” URL parameter.
This value is used for a spellchecking, i.e. if the current item language is “la-LA” then the “la-LA.tdf” dictionary will be used.
However when the item language is “en“ - Telerik control automatically interprets this value as “en-US” and used the “en-US.tdf” dictionary file.
Thus the only possible way to change the default dictionary for “en” items spellcheking is to rename the old “en-US.tdf” to something different and rename the “en-GB.tdf” file into “en-US.tdf”.
These dictionaries are located in “..\WebSite\sitecore\shell\RadControls\Spell\TDF”