Who is Mr. Vidyasagar from The Jewel in the Crown and what is their importance?

Vidyasagar is a revolutionary and acquaintance of Hari Kumar. He is a young man and defends Hari after he is wrongfully arrested after the rape at Bibighar Gardens. Vidyasagar repeatedly insists that Hari is not involved in revolutionary activities. He does not, however, pardon him from Daphne's rape.