Having joined Who in 1973, Sladen was the companion to the third and fourth Doctor (Jon Pertwee and Tom Baker) and has appeared in almost two dozen episodes. Sladen was the first character to be featured in a spinoff with K-9 and Company in 1983. Her character was recently revived in 2006, leading to a starring role in the ongoing The Sarah Jane Adventures.
Steven Moffat, writer on the new Doctor Who, released the following statement via the BBC.
"Sarah Jane Smith was everybody's hero when I was younger, and as brave and funny and brilliant as people only ever are in stories," stated Moffat. "Many years later, when I met the real Sarah-Jane — Lis Sladen herself — she was exactly as any child ever have wanted her to be."