The BJP and Mamata Banerjee's party, the Trinamool Congress, are on a rapidly-escalating collision course that has, in the last 24 hours, included vandalism and an alleged bomb attack in Kolkata. The BJP office in Hooghly, 60 km from Calcutta was set on fire this evening. The violence is the result of the arrests of two parliamentarians, Tapas Pal and Sudip Bandyopadhyay, who are senior leaders of Ms Banerjee's party, and have been accused by the CBI of involvement in a giant Ponzi scheme worth an alleged 15,000 crores that duped small investors in Bengal, where Ms Banerjee is Chief Minister.