She had summoned all her political astuteness and understanding to single-handedly unseat the Left Front from power in West Bengal, but when she was a child, Chief Minister Mamata Banerjee was so innocent that she was often backstabbed by her friends.

She had once failed in her mathematics examination due to betrayal by a 'trusted' classmate, Mamata wrote in her just-published memoirs My Unforgettable Memories while reminiscing about her childhood days.

She said her maths exam had finished 15 minutes earlier. Upon pestering by a trusted friend, she agreed to exchange the answer sheets and started solving mathematics problems on her friend's paper for the remaining few minutes.

When the bell rang, Banerjee's paper was still with her friend who submitted it to the invigilator.

"However, when the results came out, I passed with flying colours in every subject expect maths. I asked for a review and found that while I was trying to get her to pass, she had cut out all the answers in my answer sheet -- a nice way to repay a friend!" she writes in the book.

She wrote that her childhood world was mostly restricted to home, school and play and had no time for anything else, not even a wish to have a 'boyfriend'.

A spinster, she said she didn't even knew the meaning of 'boyfriend' when her friends were having an affair.

"I did not even know what the word 'boyfriend' meant and could not ask anymore. What if people misunderstood? What would they think of me?," she says while recalling how awkward she had once felt when her friends chatted with their boyfriends in her presence.