The first Kc-135 for conversion arrived
back in March.
From what I have read, the RAF had the pick of the KC-135 fleet, and picked the three lowest cycle/ hours aircraft available (it's all relative as 14833 was manufactured in '64, so will be delivered on its' 50th birthday!).
Interesting the Reg's chosen, as the R1's were XW664 on (IIRC).
RJ18/18773 ZZ664 Rivet Joint Ex USAF KC-135R 64-14833
RJ19/18778 ZZ665 Rivet Joint Ex USAF KC-135R 64-14838
RJ20/18770 ZZ666 Rivet Joint Ex USAF KC-135R 64-14830