John particularly enjoyed her role as the " totalitarian " version of Liz seen in the alternate universe in Inferno, disliking when she had to change to the normal Liz. Liz has been seen as more of an assistant than a traditional companion because she never travelled on the TARDIS. Unlike other "co-conspirator" companions, Liz serves as a bridge between the Doctor's world and the more grounded UNIT. She has also been described as more mature and equal to the Doctor than previous companions. Following John's death in 2012, then current Doctor Who showrunner Steven Moffat described Liz as "not just a sidekick but a scientist in her own right" and an example of his sentiment that "the Doctor's companions should never be his assistants – they're the people who keep him on his toes".