I believe Bertram's "I am many things to many people" explains a lot. Bertram is the leader of Tyger, Tyger but they don't know that he is also RJ. He has disciples that know him as such and as the leader of Tyger Tyger it would be pretty easy to find disciples from that pool of corrupt people. So he leads a kind of triple life as the CBI Director, the Tyger, Tyger leader and RJ.
I also believe Partridge is one of his disciples and a member of Tyger, Tyger. He had to die in the first episode of season 6 because PJ has narrowed it down and RJ doesn't trust Partridge to stand strong against PJ. Since he can identify RJ Partridge had to die. This theory would also explain the incongruities we have with RJ's description and Bertram's description. Partridge was the one that Harker knew and possibly also the one that killed Rebecca.
