During her time with the Doctor, Sarah Jane Smith proved herself a stark contrast to many of the girls who had come before her. She was confident, aggressive and stubborn, never afraid to speak her opinion and stand by it. All the same, Sarah was sensible enough to know when she couldn't cope with a situation, and was not afraid to rely on the assistance of others when she needed it. More than twenty-five years later, it appears little has changed: Sarah is still resourceful and inquisitive, and still fully appreciates her own skills, and her own limitations. But now she also has a lifetime of experiences under her belt. Will that be enough to prepare her to confront the unknown without the Doctor?

Elisabeth Sladen has played Sarah Jane since Invasion Of The Bane in January 2007. She also portrayed the character in Doctor Who from The Time Warrior to The Hand Of Fear, and in The Five Doctors, School Reunion, The Stolen Earth / Journey's End and The End Of Time.

Maria Jackson was Sarah's thirteen year-old neighbour. Despite enduring the pain of her parents' divorce, Maria found a refuge at 13 Bannerman Road -- the home of Sarah Jane Smith. Sensible, charming, resourceful and inquisitive, Maria quickly found herself a willing participant in Sarah's adventures. In many ways, Sarah Jane became Maria's surrogate mother, especially as her real mother became more concerned with trying to be Maria's friend than her parent. In many ways, Maria's love and admiration for Sarah became second only to her devotion to her father.

Yasmin Paige played Maria from Invasion Of The Bane in January 2007 to The Day Of The Clown in October 2008. She returned in The Mark Of The Berserker in November 2008.

Although essentially human, Luke Smith was created as a test subject by the alien Bane. The synthesis of ten thousand different people, Luke was born into the body of a young man -- possessed of a vast intelligence, but no understanding of popular culture or the ins and outs of being a teenager. Precocious and easily duped, Luke is gradually finding his place in the world with the help of his friends and especially Sarah Jane, who has assumed the role of his adoptive mother.

Tommy Knight has played Luke since Invasion Of The Bane in January 2007. He also portrayed the character in Doctor Who in The Stolen Earth / Journey's End and The End Of Time.

Kelsey was very much the prototypical teenager. Loud, brash, overconfident, skeptical, and boasting an addictive personality, Kelsey was also a fast friend, one who was willing to trust above and beyond her own beliefs. Although she was only a part of Sarah Jane's life for a brief time, Kelsey proved herself a valuable ally in the struggle against the Bane.

Porsha Lawrence-Mavour played Kelsey in Invasion Of The Bane in January 2007.

Alan Jackson must have thought that his life had already taken a strange turn when his marriage fell apart. Utterly devoted to his daughter, Maria, he became determined to start over again while still giving Maria a sense of normalcy and stability. Little did Alan know, Maria would soon become involved in the mysteries sought out by Sarah Jane Smith -- and, despite her best efforts, his daughter would soon enmesh him in Sarah's investigations too. A normal man caught up in extraordinary events, Alan nonetheless threw himself heedlessly into these adventures... if not for the sake of the planet, then for the sake of his child.

Joseph Millson played Alan from Invasion Of The Bane in January 2007 to The Last Sontaran in September 2008. He returned in The Mark Of The Berserker in November 2008.

Whereas Alan forced himself to assume an even greater level of maturity and responsibility in the wake of his divorce, Chrissie Jackson saw it as an opportunity to enjoy a second youth. Like Alan, Chrissie was eager to maintain close ties with Maria, but now wanted to relate to her daughter more as a friend than as a parent. More than a little shallow and self-serving, Chrissie was adamant that Maria be a regular teenager, and resented Sarah Jane's eccentric influences. Nonetheless, even Chrissie could not completely bury her maternal instincts, and she too proved that there were no lengths that she would not go to on behalf of Maria.

Juliet Cowan played Chrissie from Invasion Of The Bane in January 2007 to The Last Sontaran in September 2008.

Sarah Jane's secret weapon is Mr Smith, a highly advanced alien supercomputer. Possessed of a plummy, occasionally supercilious voice and a tendency to emerge from Sarah's attic wall with a bombastic fanfare, Mr Smith has proved to be a vital asset in the reporter's many adventures. Despite this, Mr Smith's origins are mired in deceit: he is actually an alien Xylok, who spent months covertly plotting against Sarah Jane in a bid to destroy the Earth and free his imprisoned people. Ultimately, however, Sarah was able to purge this imperative from Mr Smith's mind, and he has now resumed his place as one of her trusted allies.

The voice of Mr Smith has been provided by Alexander Armstrong since Invasion Of The Bane in January 2007. He also portrayed Mr Smith in the Doctor Who adventure The Stolen Earth / Journey's End.

Devilish, charming and a little bit full of himself, Clyde Langer is almost a typical cool kid at school -- typical except for the fact that, despite his slick exterior, he values his friends no matter how peculiarly they might act at times. Deep down, Clyde knows that he's an outsider like Maria and Luke, and he respects the bond that the three of them have formed. Still, Clyde has a streak of thoughtlessness and a tendency to be self-involved, as well as a little more curiosity than may be healthy now that he's part of the dangerous world of Sarah Jane Smith.

Daniel Anthony has played Clyde since Revenge Of The Slitheen in September 2007.

In many ways, Rani Chandra is a teenaged version of Sarah Jane herself; certainly, fortune must have been smiling on them both when the Chandra family moved into the Jackson home on Bannerman Road. An aspiring journalist with a determined streak that borders on stubbornness, Rani also shares Sarah Jane's broadmindedness and her staunch loyalty to her loved ones. Whereas Sarah Jane was a mother figure to Maria, she has become a role model for Rani -- not just someone to look up to, but also to learn from. As Rani becomes more and more involved in the fantastic life of Sarah Jane Smith -- and with her new friends, Luke and especially Clyde -- who knows what lessons life will have in store for her?

At Park Vale High School, where he is the principal, Haresh Chandra immediately established himself as a firm and unyielding disciplinarian with high expectations of the children in his charge. At times, Haresh behaves no differently at home. But there is never any doubt that, underneath his strict exterior, Haresh truly loves his family. If his treatment of Rani sometimes seems overbearing, it is only because he Haresh keenly strives to protect her from anyone and anything that might do her harm or lead her astray. How, then, would he react if he were to learn of the fantastic but dangerous adventures Rani has become involved in since meeting Sarah Jane Smith?

Rani's unfailingly cheerful mother, Gita Chandra seems almost the polar opposite of her husband, Haresh. Where he can be severe and uncompromising, she is perenially sunny and eager to please -- although this, in its own way, can sometimes be a source of annoyance and aggravation. Gita is also a hard worker, determined to put her florist's shop on the map: a trait that she has clearly passed along to her daughter.

For its second full season, The Sarah Jane Adventures once again experienced a departure from the main cast. With Yasmin Paige's education precluding her appearance in every episode, it was decided to write the Jackson family out of the programme in The Last Sontaran, although Maria and Alan would both make cameo appearances later in the year. Rani Chandra and her family were introduced to fill the void left by the Jacksons.

Meanwhile, perennial Doctor Who favourite Brigadier Lethbridge-Stewart, played once again by Nicholas Courtney, appeared in the season finale Enemy Of The Bane. This marked the fortieth anniversary of the Brigadier's first appearance in Doctor Who, and his first appearance on television since 1993.

In August 2009, Doctor Who Magazine confirmed that a fourth season of The Sarah Jane Adventures was in pre-production, but had not yet been formally commissioned. The official greenlight came on March 4th, 2010, when the BBC announced that The Sarah Jane Adventures had been renewed for two more twelve-episode seasons.

The first writer announced for the fourth season is series creator Russell T Davies (Death Of The Doctor). Davies' two-parter will guest star the Eleventh Doctor, Matt Smith, as well as Katy Manning, who played companion Jo Grant in the early Seventies. The story will also be the programme's first to be set on an alien planet.

Gareth Roberts (whose contributions have included Revenge Of The Slitheen and The Wedding Of Sarah Jane Smith) will write The Empty Planet. He will also collaborate on the season finale, Goodbye, Sarah Jane Smith, with Clayton Hickman (a former editor of Doctor Who Magazine, who cowrote From Raxacoricofallapatorius With Love with Roberts).

Also writing for the fourth season are:

• coproducer Phil Ford (The Vault Of Secrets; he has written numerous episodes, such as Enemy Of The Bane and The Eternity Trap)
• Joseph Lidster (The Nightmare Man; his previous scripts include The Mark Of The Berserker and The Mad Woman In The Attic)
• Rupert Laight (Lost In Time; he wrote The Gift)

The directors for this season will include:

• Joss Agnew (The Nightmare Man, The Vault Of Secrets, Lost In Time, Goodbye, Sarah Jane Smith; he previously directed stories such as The Last Sontaran and The Wedding Of Sarah Jane Smith)
• Ashley Way (Death Of The Doctor and The Empty Planet; he's also directed The Hungry Earth / Cold Blood for Doctor Who and episodes such as Something Borrowed for Torchwood)