This is something I've felt the show has been wrong to let linger - acknowledging the the passing of Elisabeth Sladen - since they had Eleven learn the Brigadier had passed at the end of Series Six.
In any case, this was a beautiful tribute to Ms. Sladen and Sarah Jane Smith, Dr. T! Especially in how Sarah Jane got to have the most important role in the Doctor's life: the one person trusted with his life story...at least up to just before Paul McGann's Eighth Doctor came along :D