After months of speculation and conflicting reports Jenna Coleman announced that she will return as Clara Oswald for the entirety of Series 9 of Doctor Who. In doing so she stands to become the most long-serving companion in the show's history.
Exactly how to measure the duration of a companion actor's stint on Doctor Who is a subject that I've already covered in depth previously. There are several ways to define it, but in two out of the three main ways Jenna Coleman will soon top the list.
The first is in time spent continuously on the show. The current record is held by Janet Fielding, who played Tegan Jovanka opposite the Fifth Doctor. Fielding debuted in "Logopolis" on February 28, 1981 and was with the show until "Resurrection of the Daleks" on February 15, 1984. She just narrowly beat out Elisabeth Sladen's Sarah Jane Smith for most time logged.
Jenna Coleman debuted in "Asylum of the Daleks" on September 1, 2012, though she would not reappear as a regular cast member until Christmas of that year. That means to beat Fielding's record she only needs to be on television past August 19, 2015 to be the new holder of the record. Considering that filming for Series 9 will not start until January and Orphan Black will likely hold Doctor Who's time slot until July it's a near certainty Coleman will make it when the season starts in August or September.
Another measure is number of televised adventures. Karen Gillan holds that record, having appeared as a companion in 33 stories. Jenna Coleman stands at 25 adventures with the passage of the most recent Christmas special. That means she needs only appear in nine more adventures to topple Gillan's record. This might not have happened when it was being reported that she could possibly only appear in part of Series 9, but with full season running 12 episodes usually it's virtually assured that Coleman will take this record as well.
The one record that is in no danger of being beat is that of Frazer Hines, who has appeared in more individual episodes as Jamie McCrimmon than any other companion and indeed more than many Doctors. As part of the classic, serialized era in three of the busiest seasons ever for the show, Hines has over 116 episodes under his kilt. That's not only the most of any companion, but more than every Doctor from Paul McGann to Peter Capaldi combined.
Jenna Coleman has etched herself a permanent place in Who history with her long tenure on the show. Houston Press offers her congratulations for her impending record-breaking run when the series returns.
Doctor Who returns in 2015 with "The Magician's Apprentice".