Union Public Service Commission [UPSC] — making markings on the question paper

Dear Sir

I appeared for the UPSC preliminary exam on 3rd June 2018 .
Wish to place on record of a very strange but disturbing situation I faced in the morning exam which caused a loss of about 15 minutes and my concentration .

the 1s hour of my exam i had devoted to solely reading the question paper and marking on he question paper answers i had known for sure or eliminating options so as to arrive at answers i wasn't a 100% sure of. I had made these markings with pencil. At the middle of the 2nd hour of the exam the invigilator came to my desk and told me that I was not allowed to mark with pencil on the question paper. I had only made either a tick or x on the options of the question sheet to review at end. The invigilator insisted that I erase the marking before I continue. Due to this I lost precious time and was able to complete answer of only 74 questions .

Apart from valuable time loss it caused my concentration and the ability to answer atleast another 10 -12 questions .

I was told that we are allowed to make markings on our question paper by my seniors who had given the exam in the past and I had also done in my previous attempt.

I would like your clarification on the stance as i don't believe any prudence candidate will have the aptitude to remember all the answers mentally, and strategy suggests we do atleast 2 readings before marking answers on the coded sheet

Also a clarification on whether invigilators can be made to disturb us like this

Please accept my grievance as a genuine case and see that this is addressed as this is first time