Trinamool Congress national general secretary Abhishek Banerjee left the West Bengal CID headquarters here on Thursday night after he was questioned for nearly six hours in the signature forgery case over the party's choice of Leader of Opposition in the state assembly. Banerjee reached the CID headquarters at around 5.50 pm after the Calcutta High Court granted him interim protection from any coercive action, and left the office at around 11.30 pm.