The BJP-TMC flashpoint over the Kolkata police commissioner turned into high drama this evening. Chief Minister Mamata Banerjee has started a 'Save the Constitution' Dharna after CBI sleuths turned up at the residence of Police Commissioner Rajeev Kumar, only to have cops stationed there refusing them entry. Senior police officers rushed to the spot and virtually shepherded the CBI team away from the residence. Banerjee who had defended the Police Commissioner rejecting attacks over his going missing has hit out. The CBI has been trying to locate Kumar to question him in connection with Rose Valley and Saradha ponzi scam cases with officials saying they and might arrest him as a last resort.