The star, best known for her role as Liz Shaw in Doctor Who, passed away on 5 June (12) but her death was only announced by the BBC on Twitter.com on Thursday (21Jun12).
In the message, programme bosses write, "It's with great sadness that we confirm the death of Caroline John who played (Doctor Who's) companion Liz Shaw in 1970. She passed away on the 5th June."
A funeral was held in London on Wednesday (20Jun12) but further details of John's death are unknown.
In addition to many other TV roles, John appeared in 2003 film Love Actually and also worked onstage, performing at London's National Theatre and touring with the Royal Shakespeare Company.