Existing Student Visa but not used - will it effect EC

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i wana knw if i apply for EC , i had studied in UK for my MSc but came back when i got an offered to work in my coutry , but i did got my visa extend when i was in uk cuz that time i was planning to do PhD... but later left....due to gr8 job offer...

pls suggest will it effect my ec and what kind of question they might ask ... what should i mentioned... as i geniously left and never used my visa again for travelling to uk ...